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BY THE SAME AUTHOR. 

THE YOUNG FOLKS' CYCLOPEDIA 
OF COMMON THINGS. With numerous 
Illustrations. Svo. $3.00. 

THE YOUNG FOLKS' CYCLOPEDIA 

OF PERSONS AND PLACES. With nu- 
merous Illustrations. Svo. $3.50. 

THE YOUNG FOLKS' CATECHISM OF 
COMMON THINGS. i6mo. 60 cents. 

THE YOUNG FOLKS' ASTRONOMY. 

Illustrated. i6mo. 60 cents. 

THE YOUNG FOLKS' HISTORY OF 

THE WAR FOR THE UNION. With nu- 
merous Illustrations. i2mo. {In September.') 



THE 



YOUNG FOLKS 



ASTRONOMY 



BY 

JOHN D. CHAMPLIN, Jr., 

LATE ASSOCIATE EDITOR OF THE "AMERICAN CYCLOPEDIA" 

ILLUSTRATED 







' 






NEW YORK 
HENRY HOLT AND COMPANY 



„* 



Copyright, 1881, 

by 

HENRY HOLT & CO. 



J. Campbell, 

printer. 

15 Vaiidewater St., N. Y. 



PREFACE. 



The commendation which the astronomical 
articles in the Young Folks' Cyclopaedia of Com- 
mon Things have received from parents and 
teachers has led to the preparation of this little 
volume, in the hope that it will fill a want long 
felt in homes and schools. There can be little 
question of the propriety of early grounding a 
child in an elementary knowledge of the astro- 
nomical features of the earth on which he lives 
and of the universe of which it forms a part ; yet 
it is almost impossible to find a text-book in 
which either the language or the ideas are within 
an ordinary child's comprehension, most of the 
books miscalled astronomy " primers" being fit- 
ted only for those who already possess some 
knowledge of the science and of its correlated 
subjects. In the present work the topic is treated 
in the most elementary way, the child being first 
taught that the earth is a heavenly body which 
moves in the heavens in the same way as the 
moon, and which would look from the moon at 
night much as the moon looks to us. From this 



IV PREFACE. 

his mind is gradually led up to a contemplation 
of the other heavenly phenomena, such as the 
movements of the bodies of the solar system, and 
what results from them; then of the fixed stars 
and the constellations, and lastly of some of the 
practical uses of astronomy, such as the measure- 
ment of time and the calendar. Abstruse calcu- 
lations and the use of expressions requiring a 
knowledge of mathematics have been avoided, 
and even numbers denoting celestial distances 
so great as to mean nothing to a child, have been 
made intelligible by comparison with some known 
measure of length on the earth. The language 
used is simple, technical phrases have been ex- 
plained, and pictorial illustrations introduced 
wherever they tend to make the text clearer and 
more intelligible. 

It is perhaps not improper to add that the 
work was submitted, before printing, to the crit- 
icism of two eminent teachers, who approved of 
its general method and expressed a belief that it 
is well adapted for teaching. 

J. 1). C, Jr. 

New York, May, 1881. 



TABLE OF CONTENTS. 



LESSON I. 

PAGE 

Astronomy and what it Teaches i 

LESSON II. 
What the Ancients knew about the Earth 7 

LESSON III. 
How we know that the Earth is Round 13 

LESSON IV. 
About the Size of the Earth 21 

LESSON V. 
The Earth in the Heavens 27 

LESSON VI. 
The Attraction of Gravitation 33 

LESSON VII. 
The Earth Turns Round 40 

LESSON VIII. 
The Earth Turns Round once a Day 47 



IV CONTENTS. 

LESSON IX. 

PAGE 

The Turning of the Earth causes Day and Night 53 

LESSON X. 
The Earth Moves Round the Sun 58 

LESSON XI. 
The Earth's Orbit 65 

LESSON XII. 
Why the Days and Nights are Unequal. . . 71 

LESSON XIII. 
The Changes of the Seasons 80 

LESSON XIV. 
Climate and the Zones of the Earth 86 

LESSON XV. 
The Sun 93 

LESSON XVI. 
The Moon and its Phases 104 

LESSON XVII. 
What the Moon is like 114 

LESSON XVIII. 
Eclipses of the Moon 121 



CONTENTS. V 

LESSON XIX. 

PAGE 

Eclipses of the Sun , 128 

LESSON XX. 
The Solar System 136 

LESSON XXI. 
Motion of the Planets in their Orbits 144 

LESSON XXII. 
The Lesser Planets 153 

LESSON XXIII. 
The Greater Planets 163 

LESSON XXIV. 
Comets and Shooting Stars 174 

LESSON XXV. 
The Fixed Stars 185 

LESSON XXVI. 
The Appearance of the Heavens 194 

LESSON XXVII. 
The Constellations 203 

LESSON XXVIII. 
The Julian Calendar . 214 

LESSON XXIX. 
The Gregorian Calendar 221 



YOUNG FOLKS' ASTRONOMY. 



LESSON I. 

ASTRONOMY AND WHAT IT TEACHES. 

Astronomy is the science which tells about 
the heavenly bodies and their movements. 
To understand what it teaches it is first 
necessary to know what the heavenly bodies 
are. 

Every child is astonished on being- told for 
the first time that the stars are not small 
lights, but are large bodies — nearly all of 
them much larger than our whole world, and 
that many of them are much like our world, 
and perhaps are covered like it with living 
things. He is still more astonished when 
he is told that our world, or the earth on 
which we live, is a round ball made up of 
much the same matter as the stars. Yet we 
know that these things are true, because they 



2 YOUXG FOLKS' ASTRONOMY. 

have been proved to be so in ways which will 
be told about in other parts of this book. 
We know that the stars and our earth are 
large round bodies, which are always moving 
in the heavens , and for this reason they, to- 
gether with the sun and the moon, are called 




i. The Earth as seen from the Moon. 

the heavenly bodies. It may be at first hard 
to think of the earth, which looks flat to us, a$ 
a heavenly body like the sun, the moon, and 
the stars, which appear to float in the heavens 
upheld by nothing; but it will not seem so 
strange when it is shown, as it soon will be, 
that our earth moves through the heavens 



ASTRONOMY— WHAT IT TEACHES. 3 

touching nothing but the air around it. If it 
were possible to see the earth from the moon, 
it would look to us much like the moon, only 
it would be larger and the dark and light 
parts would show different shapes from those 
which we see on the moon's surface. In the 
picture (i), which shows one side of the earth 
as it would look from the moon, the light 
parts are Europe, Asia, and Africa, and the 
dark parts the ocean. 

Astronomy is one of the most important 
and most useful of studies. By means of it 
we can measure time correctly, and tell be- 
forehand what the movements of the heavenly 
bodies will be. We are thus enabled to make 
almanacs which give the times of the rising 
and setting of the sun and the moon, the 
rising and falling of the tides, and other use- 
ful information. 

By means of astronomy also we know much 
about the earth which could not otherwise be 
known, and are able to make maps on which 
are correctly shown the situations of its lands 
and seas, and of towns, rivers, and mountains. 
For as different stars must be seen from 
different places on the earth, if an astronomer 
were carried blindfolded to the most distant 
part of the earth, and placed with his instru- 



4 YOUNG FOLKS' ASTRONOMY. 

ments on a rock in the middle of the ocean, 
he could tell, in a few minutes, by studying 
the stars, exactly where he was. Thus the 
sailor knows from the stars where his ship is, 
and is enabled to steer his way safely across 
the great oceans. 

Astronomy too has made men braver .and 
better than they were in old times. When 
the causes of the movements of the heavenly 




2. Medal of the Great Comet of 1680. [Newcomb and 
Holden's Astronomy.] 

bodies were not understood, men worshiped 
the sun as a god, and were filled with awe 
and dread when it was darkened, for they be- 
lieved that their god was angry with them ; 
and when they saw a comet flaming in the 
sky, they thought it to be the forerunner of 
war, sickness, or famine. In 1680 a very bright 
comet appeared, and the people in Europe 
were so frightened at it that a medal like the 
picture (2) was struck in Germany- to quiet 



ASTRONOMY— WHAT IT TEACHES. 5 

their fears. The inscription on the back is, in 
English: " The star threatens evil things ; trust 
only ! God will turn them to good." Happily 
we are free from such silly notions, for our 
knowledge of astronomy has taught us that 
each one of the heavenly bodies forms a part 
of a great system called the universe, which 
is governed by laws that never change. 

RECITATION FOR LESSON I. 
What does astronomy tell about ? 

The heavenly bodies and their movements. 

What are the heavenly bodies ? 

The earth, the sun, the moon, and the stars. 

What does astronomy enable us to do ? 

To measure time correctly, and to tell in 
advance the movements of the heavenly 
bodies. 

Of what use are these things to us? 

They enable us to make almanacs and 
maps. 

What are almanacs good for? 

They give us the time of the rising and 
setting of the sun and the moon, the rising 
and falling of the tides, and other useful infor- 
mation. 

How does astronomy aid us in making maps ? 

It enables us to lay down correctly on them 



6 YOUNG FOLKS' ASTRONOMY. 

the situations of lands and seas, and of town.-?, 

rivers, and mountains. 

Eow does astronomy aid the sailor? 

By studying- the stars he can tell exactly in 
what part of the sea his ship is, and can thus 
find his way safely across the great oceans. 

How does a knowledge of astronomy make men better 
and braver than they were in old times ? 

It teaches them the causes of the move- 
ments of the heavenly bodies, so that they no 
longer fear them. 



LESSON II. 

WHAT THE ANCIENTS KNEW ABOUT THE 
EARTH 

People have not always known as much as 
we do about the earth. In the earliest ages 
of which history tells, there were learned 
men who taught that it is round, but this was 
by no means generally believed. Little was 
known in ancient times of the surface of the 
earth. America and Australia had not been 
discovered, and even the greater parts of 
Europe, Asia, and Africa had not been ex- 
plored. As far as travelers had gone, 
whether on land or sea, more land and more 
water were seen beyond, and so it came to 
be the belief of almost every one that the 
earth was nearly flat, tliat it was surrounded 
by the waters of the ocean, and that the 
heavens hung over it like a dome. Some 
thought that this great island floated in the 
water, some that it had long roots which 
stretched downward without end (3), and 
others that it was held up by many strong 
columns or pillars (4). 



8 YOUNG FOLKS 1 ASTRONOMY. 

The ancient Hindoos, or people of India, 
had still more singular notions about the 
earth. They believed that it was shaped like 
a hemisphere (Greek hemi, half, and sphaira, 
sphere) — that is, like the half of a sphere or 
globe — and that it rested with its round side 
upward, as shown in the picture (5), on the 




3. Ancient Idea of the Earth with Roots. 

heads of four elephants standing on an im- 
mense turtle, which floated on the sea. 

The ancients had many ways of explaining 
the rising and setting of the sun. Some 
thought it to be a great ball of fire which was 
put out by the waters of the ocean when it set 
and which was lighted again when it rose in 
the morning after passing through the waters 



THE ANCIENTS AND THE EARTH 9 

beneath the earth ; others thought that it 
passed through a tunnel under the earth; 
and still others, who believed that the earth 
was held up on columns, thought that the 
sun went between them. All these things 
seem very laughable to us, who know that 
the earth is really round like a ball, and that ■> 




4. Ancient Idea of the Earth on Columns. 

it is not held up by any solid thing, but floats 
in the heavens, just as the moon does ; but 
we must remember that it has taken thousands 
of years to find out all that we know about it. 
We must remember, too, that the earth, at 
first sight, really appears to be flat, and that 
the heavens look like a dome above us. This 



YOUNG FOLKS' ASTRONOMY, 



is the same wherever on the surface of the 
earth we may happen to be. If we are in a 
hilly country, we see all around us hills whose 
tops the heavens appear to touch ; and if 
we walk to the top of the hills, more hills are 
generally seen beyond, with the dome of the 
heavens reaching down to them. If we stand 




5. The Hindoo Idea of the Earth. 

in the middle of a flat country, we still see 
the heavens shutting in the land on all sides, 
and meeting it in a line which is broken only 
by the hills, trees, or houses which may be in 
sight ; and it is the same at sea, where there 
are no hills, trees, nor houses to shut out the 
view — the waters stretching out like a great 



THE ANCIENTS AND THE EARTH. II 

plain meet the sky all around. The line 
where the earth and the sky appear to meet, 
whether on land or water, is called the 
horizon (Greek, limit or bounding line). 

RECITATION FOR LESSON II. 
Did the ancients know as much about the surface of 
the earth as we do ? 

No ; they knew nothing of America and of 
Australia, and very little even of Europe, 
Asia, and Africa. 

What did they think of the shape of the earth ? 

Most people believed that it was a nearly 
flat island, with the heavens hanging over it 
like a great dome. 

How did they think the earth was held up ? 

Some thought that it floated in the water, 
some that it had long roots, and others that 
it was held up by many strong columns. 

Did not the Hindoos have a different notion about it? 

Yes ; they believed that it was shaped like 
a hemisphere, and that it rested on the heads 
of four elephants standing on a great turtle, 
which floated on the sea. 

"What do you understand a hemisphere to be ? 

The half of a sphere or globe. 

How did the ancients explain the rising and the setting 
of the sun ? 

Some thought it was a great ball of fire 



12 YOUNG FOLKS' ASTRONOMY. 

which was put out by the waters of the ocean 
when it set, and lighted again when it rose 
out of the waters in the morning ; some 
thought it passed under the earth through a 
tunnel ; and those who believed that the 
earth was held up by columns thought it 
went between them. 

Does not the earth really appear to be flat ? 

Yes; wherever we go, on land or sea, it 
looks like a great plain broken by hills and 
valleys, with the sky stretching over it like a 
dome. 

What do we call the line all around us where the earth 
and the sky appear to meet ? 

The horizon, which means the limit or 
bounding line. 



LESSON III. 

HO W WE KNO W THA T THE EAR TH IS RO UND. 

Wherever we happen to be, we always 
see the horizon around us ; and if we go in 
any direction from a place, things not seen 




6. The Flies' Horizon. 



before come into view in the distance, while 
the horizon always appears to be just as far 
off. This is because the earth is round, and 
as we travel nearer and nearer to things they 



14 YOUNG FOLKS' ASTRONOMY. 

appear to rise up from below the horizon 
over its rounded edge. 

This will be best understood by looking at 
the picture (6) of the two flies on an orange. 
Suppose first that one fly is standing still on 
the side of the orange at A, and another on 
the other side at C. The one at A cannot see 
the one at C, on account of the roundness of 
the orange (earth), which shuts out the view ; 
but if A should travel up to B, it could then 








7. The Horizon seen from the foot of a Mountain. 

look over the rounded edge and see the one 
at C. 

The two pictures (7 and 8) show how one can 
see further over the edge of the earth from 
the top of a mountain than from its base. 
The curved figure 55 (7) is a part of the 
rounded surface of the earth, on which is seen 
a mountain, M; houses K, L, and V; woods, IT, 
X, and Y ; and a river, R. If we were stand- 
ing near the foot of the mountain at M, we 



THE EARTH IS ROUND. 1 5 

could see on our right only to A, and on our 
left only to E, because all things further away 
than those points would be below the round 
edge of the earth, and only the sky would 
appear beyond. In front we could see to B, 
C, and Z>, and if tne mountain were not there 
we could see the same distance behind. The 
dotted line ABCDE then would be our hori- 
zon, or the line where earth and sky appear 
to meet. 




\ 

8. The Horizon seen from the top of a Mountain. 

But if we go up the mountain and stand 
on the top of it at N (8), we can then see 
much further than before, and our horizon 
will be at FGHIJ, instead of at ABCDE, 
From our first position we could see only the 
house K and the top of the house L, and a 
part of the wood W; but from the mountain 
we can see not only these, but the rest of the 
wood W, all the wood X, and part of that at 



1 6 YOUNG FOLKS' ASTRONOMY. 

Y, a larger part of the river R, and the houses 
at L and V. The rest of the wood Y and the 
other parts below the line FGHIJ will still 
be out of sight, because they are below the 




9. Ships Above and Below the Horizon. 

rounded edge of the earth ; but if we could 
go higher than the top of the mountain, we 
could see still further, for the higher we are 
above the surface of the earth the further 
over the edge we can look. 



- THE EARTH IS ROUND. 1 7 

That the earth is round is shown on the 
sea still better than on the land, because there 
are no hills, trees, and houses to shut out the 
view. 'If we watch ships in the distance just 
coming into view, we shall see first the tops 
of the masts, then the sails will come into 
sight little by little, and lastly the hull will 
come up over the edge. In the picture (9) are 
shown several ships, some in full view, and 
some just going down or coming up over the 
edge of the earth. In the same way, if we 
watch a ship sailing away from us, we shall 
see the hull first go out of sight, and then 
the masts and the sails go down little by little 
until at last all will disappear. If the sea 
were flat the whole of the ship would stay in 
sight, and all would gradually grow dimmer 
and dimmer until it faded entirely from 
view. 

But the best proof that the earth is round 
is that men have traveled round it. About 
three hundred and fifty years ago (15 19), a 
Portuguese named Magalhaens, or Magellan, 
in the service of the King of Spain, sailed in 
search of the Moluccas, or Spice Islands. 
After passing through the strait at the south 
end of South America, called after him the 
Strait of Magellan, he sailed westward across 



1 8 YOUNG FOLKS' ASTRONOMY. 

the Pacific Ocean until he came to the 
Philippine Islands. He was killed on one of 
these islands in a fight with the natives, but 
his ship, the Vitoria (Victory), kept oh going 
west, and in three years after leaving Spain 
returned there (1522), having sailed entirely 
around the earth. 

Since then this voyage has been made a 
great many times, and as it now takes, by the 
aid of railroads and steamships, only about 
three months to go round the earth, many 
people make the trip for pleasure. This 
proves that the earth is round and not flat, 
for by traveling in a straight line always in 
one direction we finally come back to the 
place we started from, just as a fly creeps 
round an orange ; but if the earth were flat, 
the further we traveled in a straight line the 
further we should be from the point we started 
from. 

But, it may be asked, could not one travel 
round the earth if it were oval or egg-shaped? 
Yes ; but we know that it is not very oval, 
but more round like a ball, because its shadow 
is round. The shadow of a thing is always 
like the thing itself ; for instance, if you hold 
up a square thing, like a book or sheet of 
paper, between a lamp and the wall, it will 



THE EARTH IS ROUND. 1 9 

cast a square shadow on the wall ; an oval 
thing, like an egg, will cast an oval shadow ; 
and a round thing, like an orange or a ball, 
a round shadow. Now, there are certain 
times, which will be told about by and by, 
when the shadow of the earth can be seen, 
and it is always nearly round ; and from this 
we conclude that the earth itself is nearly 
round as an orange is. 

RECITATION FOR LESSON III. 

Why is it, when we go in any direction from a place, 
that things not seen before appear to rise up into 
view in the distance? 

Because as w r e travel nearer and nearer to 
them they come into view over the rounded 
edge of the earth. 

Why can we see more from the top of a mountain than 
from its foot ? 

Because the higher we get, the further over 
the rounded edge of the earth we can see. 

How does the sailing of a ship prove that the earth 
is round ? 

When a ship is coming in from sea, the tops 
of the masts are first seen, and last of all the 
hull comes up into sight. 
Why does not the hull come into view at the same 

time with the masts? 

Because when the tops of the masts are 



20 YOUNG FOLKS' ASTRONOMY. 

first seen, the hull is below the rounded edge 
of the earth. 

Would it not look the same if the sea were flat ? 

No ; if the surface were flat, the whole of 
the ship would come into view at once. 

What still better proof is there that the earth is round ? 

That men have gone entirely around it by 
traveling always in one direction. 

Could they not do this if the earth were egg-shaped? 

Yes ; but we know that it is not egg-shaped, 
because we can sometimes see its shadow,- 
and it is nearly round like the shadow of a 
sphere or ball. 



LESSON IV. 

ABOUT THE SIZE OF THE EARTH. 

It may be thought that though the earth's 
roundness seems to be proved, it is hardly 
fair to call it round like an orange, because 
an orange is smooth, while the surface of the 
earth is very rough and uneven in places. 
But the earth is just as smooth for its size as 
an orange is, for the hills and mountains on 
its surface are no larger in proportion than 
the rough places on the skin of the orange. 
Indeed, the earth is much smoother for its 
size than an orange, because if the orange 
were made as large as the earth, and the 
roughnesses on its skin were made large in 
proportion, they would be very much higher 
and rougher than the highest mountains on 
the earth. 

There are higher mountains on the moon 
than on the earth, in proportion to its size, 
yet the moon looks to us like a round, smooth, 
bright ball, with some dark patches on it; 
and if we could get as far away from the 
earth as we are from the moon, it also would 



22 YOUNG FOLKS' ASTRONOMY. 

look much the same to us, for we would not 
be able to see its roughnesses. 

If the mountains on the earth are, then, so 
small in proportion to its size, the earth must 
be very large. That it is so is proved by the 
fact that its surface, which we know is round- 



b/ 

/ 












\ 

\ 

V 


\ 












i 

1 

/ 


\ 

\ 












/ 

/ 


0. Show- 


ing 


that 


a Curve 


is 


part of 


a Circle 



ed, appears flat to us. If we stand in the 
middle of a great plain, or on a ship at sea, 
we cannot see any curve, though we can look 
many miles in every direction. From this it 
is clear that the curve must be very slight, 
and the circle of which the curve forms a 
part very large. 



SIZE OF THE EARTH. 23 

This will be understood better by laying a 
piece of hoop on the ground, and marking 
the curve around until the two ends meet. 
In the picture (10), AB is a piece of hoop, large 
enough to show the curve, and CDE is the 
curve continued ail the way round. We 




11. Showing that the flatter the Curve is, the larger must 
be the Circle of which it is a part. 

shall easily see from this that a curve is only 
a part of a circle, and the next picture (11) will 
show us that the flatter the curve is, the larger 
must be the circle of which it is a part. 

Now, the curve of the earth's surface is so 
nearly flat that we who stand on the surface 
cannot see that it is round at all ; if it were 



24 



YOUNG FOLKS' ASTRONOMY. 



continued, therefore, round the earth until 
the two ends met, it would form a very 
large circle. In fact, we know exactly the 
size of this circle, for it has been very care- 
fully measured ; it is nearly twenty-five thou- 
sand (25,000) miles. It may be hard at first 



£UMFERENC£ 




12. Circumference and Diameter. 



to understand how great a distance this is, 
but perhaps we may get some idea of it when 
we think that if we should walk ten miles 
every day it would take us nearly seven years 
to go round the earth. 

If, again, a straight line should be drawn 
from the surface of the earth through its 



SIZE OF THE EARTH. 2$ 

centre to the surface on the other side, it 
would measure about eight thousand (8,000) 
miles. A measurement thus made through 
the earth is called its diameter ; and a meas- 
urement made round the earth in a great 
circle is called its circumference. 

RECITATION FOR LESSON IV 

Some parts of the earth's surface are very rougn and 
uneven : is it proper to call the earth at those parts 
round? 

Yes ; because the earth is so very- large 
that the highest mountains on its surface are 
not so large in proportion as the rough places 
on the skin of an orange. 

How would the earth look from the moon ? 

Like a round, smooth ball, with some dark 
patches on it, much the same as the moon 
looks to us. 

How do you know that the earth is very large ? 

Because its surface, which is curved or 
rounded, is so large that it looks flat to us. 

How has the size of the earth been found out ? 

By measuring a part of the curve, and then 
by continuing the curve round until the two 
ends met and formed a circle round the earth. 

What is the length of this circle ? 

Nearly 25,000 miles. 



26 YOUNG FOLKS' ASTRONOMY. 

What is such a measurement made round the earth or 
round any other circle called ? 

Its circumference. 

What is the length of a straight line drawn through the 
centre of the earth, from one side to the other ? 

About 8,000 miles. 

What is such a measurement made through the eaith 
or any other round thing called ? 

Its diameter. 



LESSON V. 

THE EARTH IN THE HEAVENS. 

We have thus learned that the earth is a 
globe or sphere, and that it is very large ; we 
have now to find out what holds it up in the 
heavens. But is it necessary to suppose that 
it is held up by anything ? We see the sun, 
the moon, and the stars above us, with noth- 
ing solid to hold them up ; and why should 
not the earth hang in the heavens like them, 
touching nothing and upheld by nothing 
which can be seen. Indeed, we know that 
this is so, for wherever we go on any part of 
the surface of the earth we always see the 
heavens above, with nothing solid between 
them and the earth. 

It must be clearly understood that the 
heavens mean something more than the air 
* in which we see the clouds float. The air, 
which covers the earth like an envelope on 
every side, and which, when taken together, 
is called the atmosphere (Greek, atmos, air, 
and sphaira, a sphere), does not reach up very 
high. Air thick enough to breathe lies only 



28 YOUNG FOLKS' ASTRONOMY. 

two or three miles deep on the surface of the 
earth, and above that it grows thinner and 
thinner until it seems to fade into nothing. 
But beyond that, reaching away millions on 
millions of miles through space, stretch the 




13. The Earth in the Heavens. 

heavens, in which are the sun, the moon, and 
the stars. 

The air or atmosphere, then, is a kind of shell, 
which covers the whole surface of the earth, as 
seen in the picture 13, where it is shown many 



THE EARTH IN THE HEAVENS. 29 

times thicker in proportion than it realty is. 
Some think that it is only about fifty miles 
thick, which is really very little, when com- 
pared with the thickness of the earth ; and it 
is scarcely anything when compared with the 
great heavens ; yet it is this little shell of air 
around us which makes the heavens look to 
us like a dome. In clear days this vault looks 
blue, because the air, which appears to us to 
be clear, is slightly blue when taken in large 
masses ; and in misty weather it looks whitish 
or grayish, according to the clouds floating 
in the air. In the night, when the atmosphere 
is clear, the sky does not look to us so much 
like a dome, and we can see the stars shining 
so far away in the black heavens that they 
look like twinkling specks of light. 

It has been said that wherever we go on 
any part of the surface of the earth we always 
see the heavens above us. One may exclaim, 
Flow can the heavens be above a person stand- 
ing on the opposite side of the earth from 
us ! Would it not be more proper to say 
below ? No ; it would not be proper to say 
below, because the heavens would appear to 
him on his side of the earth just as they do to 
us on our side, and we are as much upside 
down to him as he is to us. Since the earth 



30 



YOUNG FOLKS' ASTRONOMY. 



is a globe, the words up and down cannot be 
used to mean the same real direction to 
persons on all sides of it. The term up 
means simply from the earth's centre, while 



% 



V* 



^ 



^? 




14. Men on different sides of the Earth. 



down means toward the earth's centre. A 
person in China, which is on the opposite 
side of the earth from us, would use the word 
up just as we do here, and to mean the same 
thing, but his up would be in a direction just 



THE EARTH IN THE HEAVENS, 3 1 

opposite to ours. So to every one on the 
earth, no matter on what side of it he may be, 
;// means from the centre of the earth toward 
the heavens, and down means toward the 
centre of the earth ; and the heavens are 
always above and the earth always below 
him. The reason of this is hard to under- 
stand, but it will be made clearer further on. 

RECITATION FOR LESSON V. 

What holds the earth up in the heavens ? 

It is not held up by any solid thing, but. 
floats in space like the sun, moon, and stars. 

How do you know this? 

Because wherever we go on the earth's 
surface we always see the heavens above us, 
with nothing solid between them and the 
earth. 

When you speak of the heavens, do you mean the air 
or atmosphere? 

No ; the atmosphere does not reach up very 
high, and forms only a very small part of the 
great heavens, in which are the sun, the moon, 
and the stars. 

What causes the heavens to look in the day-time lik:v 
a great blue dome reaching down to the earth on. 
all sides ? 

The atmosphere, because the air is blue. 



-32 YOUNG FOLKS' ASTRONOMY. 

Do the heavens look the same in the night-time? 

No ; when the heavens are black at night 
they do not look so much like a dome. 

You speak of the heavens above us; if you were on 
the opposite side of the earth would you say the 
heavens below us? 

No ; because the heavens would look the 
same there as they do here. 

How can you explain this? 

As the earth is a globe, the words above 
and below, or up and down cannot mean the 
same real direction to persons on all sides of 
it. Above and up mean simply from the 
earth's centre, and below and down toward 
the earth's centre. 



LESSON VI. 

THE ATTRACTION OF GRAVITATION. 

When we hold a stone in our hand it feels 
heavy, and we say that it has weight ; if we 
drop it, it falls to the ground, and we say 
that it falls because it has weight. This is 
true, but what is this which we call weight ? 
Why are things heavy ? 




15. Iron-filings drawn by a magnet. 

If a magnet be held near to a mass of iron 
filings, the little pieces of iron will be attracted 
or drawn toward it and will collect in a clus- 
ter on its end. We cannot see anything be- 
tween the magnet and the iron filings to make 



34 YOUNG FOLKS' ASTRONOMY. 

them go to it, yet we can see that they are 
drawn to it by some force which though in- 
visible is strong. If, now, a small magnet be 
held near a large mass of iron, the magnet 
will be drawn to the iron just as the iron 
filings were drawn to the magnet. The iron 
i is really drawn by the magnet as much as the 
magnet is drawn by the iron, but the iron 
being so much the larger overcomes the mag- 
net and makes it come to it. 

Every thing on the earth attracts or draws 
toward itself every other thing, much as the 
magnet draws the iron filings to itself ; but as 
the larger the thing is the more it attracts, 
and as the earth itself is much larger than 
anything on it, it attracts or draws toward 
itself everything on it with so great a force 
that it will not let most little things go toward 
each other. We cannot see anything between 
the earth and the things which are drawn 
toward it any more than we can between the 
magnet and the iron filings, but the attraction 
is just as real in the earth as in the magnet. 
It is, however, a different kind of attraction 
from that of the magnet, for the magnet draws 
the iron filings more than the earth does, as 
it keeps them from going to the earth ; but 



ATTRACTION OF GRAVITATION. 35 

this is true of iron only, all other things being 
attracted more by the earth. 

Thus the earth is always drawing every- 
thing to itself. The force with which it does 
this is called gravitation, or the attraction of 
gravitation, which causes what we commonly 
call weight ; and when we say that a thing is 
heavy, we mean simply that it has gravity, 
or is drawn toward the earth by the force of 
gravitation. Now, some things are attracted 
toward the earth much more strongly than 
other things ; and when a thing is drawn 
strongly we say it is heavy, and when it is 
drawn with but little force we say it is light. 

If it were not for the attraction of gravita- 
tion we should have no seas, lakes, nor rivers, 
for all the water on the earth is kept in its 
place by this force. The atmosphere, too, is 
held around the earth by the same force, else 
it would all fly away and become scattered 
throughout the heavens. 

When we drop a stone it falls in a straight 
line to the earth. The direction of this line 
can easily be seen by tying a string to a stone 
and raising the stone up a little ; the stone (16) 
is drawn downward by the attraction of gravi- 
tation, and this draws the string into a straight 
line, which, if it could be continued down 



36 



YOUNG FOLKS ASTRONOMY. 




through the earth would pass directly through 
its centre. This would be the same, no matter 
on what part of the earth's surface we might 
stand. In the picture (17) are shown four per- 
sons standing on different sides of the earth, 
each one holding such a 
string in his hand ; it will 
be seen that the dotted 
lines drawn straight from 
each string meet in the 
centre. So all things 
which fall anywhere on 
the earth always go to- 
ward the same point — 
that is, toward the centre 
of the earth. 

You can now under- 
stand why down always 
means toward the centre 
of the earth, and up, on 
T r '«. • ^ . a. any part of the surface of 

16. Showing that a Stone J * 

falls in a straight line to the earth, always means 
the Earth - toward the heavens ; and 

also why persons on the opposite side of the 
earth from us do not fall off, but live there as 
easily as we do on our side; their natural 
position is just the same as ours, with the feet 
upon the earth and the head toward the heav- 



ATTRACTION OF GRAVITATION. 



37 



ens, and they are held in their places just as 
we are in ours, by the attraction of gravita- 
tion, which draws everything toward the cen- 
tre of the earth. 

The attraction of gravitation was first found 




17. Showing that the line made by anything in falling, 
would go, if continued, to the centre of the Earth. 

out by Sir Isaac Newton, a famous English- 
man. While sitting in his garden one day, 
he saw an apple fall from a tree. This set 
him to thinking what made it fall, and he soon 
made up his mind that all things on the earth 
are drawn alike toward the centre of the 



38 YOUNG FOLKS' ASTRONOMY. 

earth ; and by making many experiments he 
found out that this is true. 

RECITATION FOR LESSON VI. 

If a magnet be held near some iron filings, what will 
happen ? 

The pieces of iron will be attracted or 
drawn to the magnet. 

If a small magnet be held near a large mass of iron, 
what will happen? 

The magnet will be drawn to the iron. 

What do you learn from this ? 

That the larger draws the smaller to itself. 

Is this true of other things on the earth? 

Yes ; all things on the earth are attracted 
or drawn toward each other, but by another 
kind of attraction. 

Are they all attracted equally? 

No ; the larger the thing is the more it 
attracts or draws things toward itself. 

What attracts more than anything else ? 

The earth, because it is much larger than 
anything on it. 
What is this force which draws things to the earth 

called? 

The attraction of gravitation. 

What is meant when a thing is said to be heavy? 

It is meant that it has gravity, or is drawn 
toward the earth by the force of gravitation. 



ATTRACTION OF GRAVITATION. 39 

What would happen to things on the earth if there were 
no gravitation ? 

Seas, rivers, and lakes would not stay in 
their places, and the air would fly away and 
b3 scattered through the heavens. 

When we drop anything, in what direction does it fall ? 

Toward the centre of the earth. 

13 this the same everywhere on the earth's surface ? 

Yes ; because the attraction of gravitation 
draws everything on the earth toward its 
centre. 
Who first found out the attraction of gravitation ? 

Sir Isaac Newton. 



LESSON VII. 

THE EARTH TURNS ROUND. 

We have thus learned that the earth is a 
great globe which floats in the heavens ; we 
have now to find out whether it moves or is 
at rest. 

When we watch the other heavenly bodies 
they appear to move around the earth, which 
seems to us to be at rest. The sun appears 
to rise in the east in the morning, pass through 
the heavens over our heads, and set in the 
west in the evening. The moon appears to 
follow the same course ; and if we watch the 
stars on a clear night, we shall see those in 
the east rising up little by little above the 
edge of the earth, and those in the west 
gradually sinking down below the horizon. 
Thus, while the earth seems to be still, all the 
heavenly bodies above, the sun, the moon, 
and the stars alike, appear to be moving 
through the heavens from east to west in 
curves or rounded paths, which, if continued 
all round the earth, as we marked round the 
curve of the piece of hoop (10), would form 



THE EARTH TURNS ROUND. 



41 



circles. This is what is called the apparent 
movement of the heavenly bodies, because 
they appear to move round the earth in these 
paths. 

There are two ways of explaining- this: 
first, we may explain it as the ancients did, 
by saying that the earth stands still, while the 




The apparent movement of the Sun. 



sun and the stars move round it in circles ; 
and second, by saying that the earth itself is 
all the while turning round. 

We now know that the first cannot be true. 
If it were true, the sun and the stars would 
really move round us, as they appear to do, 
once every twenty-four hours. But the sun 
is many hundred thousand times larger than 



42 YOUNG FOLKS' ASTRONOMY. 

the earth, and many of the stars are as large, 
and probably larger than the sun, as will be 
told about hereafter ; and it seems absurd to 
think that these immense globes should turn 
around our earth, which, though it seems 
large to us, is really very small when com- 
pared with the other heavenly bodies. The 
sun, too, as you will learn by and by, is many 
million miles away from the earth, and the 
stars are so much further away that we can 
not even count the distance. Now, the fur- 
ther they are away from the earth the larger 
must be the circles in which they move round 
it, and the faster they must go to get round 
it in the twenty-four hours. If we suppose 
them to move round the earth, we must be- 
lieve that they travel through the heavens at 
a speed so great that our minds can scarcely 
think of it. But it does not seem reasonable 
to believe this. 

Suppose, now, that the earth turns round 
in a way opposite to that in which the other 
heavenly bodies appear to move — that is, 
from west to east. The apparent move- 
ments of the heavenly bodies can then be 
easily explained : the sun will then appear 
to rise in the east and to set in the west, as 
if it really moved round the earth, and the 



THE EARTH TURNS ROUND. 43 

stars will look as if they followed the same 
course. 

Let us try to make this plainer. Set a 
lamp upon the table to represent the sun. 
Stick a knitting-needle through the centre of 




19. The motion of the Earth shown with an orange. 

an orange, and call it the earth. If we hold 
it as shown in the picture, and turn it found 
and round by twisting the needle moving the 
orange always from left to right, the light of 
the lamp will shinex>n every side of it in turn, 



44 YOUNG FOLKS' ASTRONOMY. 

moving round it from right to left, or the 
opposite way from that in which the orange 
turns. Stick a pin in one side of the orange 
and suppose it to be a man standing on any 
part of the earth ; then turn the orange round 
until the light of the lamp strikes it ; this will 
be sunrise at that place on the earth, and if 
you keep on turning, by and by the pin will 
come into shadow again, which will be sunset 
at that place. The man (pin) on the earth 
(orange) will really move round with it, while 
the sun (lamp) stands still, but the sun will 
look to him exactly as if it moved, and he will 
seem to himself to stand still. 

Thus we, who are upon the earth, are all 
the while moving round with it, and the sun 
and the stars come into our view and then pass 
out of it as we spin round. Our movement 
being from west to east, things appear to 
move in the opposite direction, because as 
the eastern edge of the earth goes down they 
come into sight above it, and we then keep 
on moving by them until the western edge of 
the earth shuts them out of our view. 



THE EARTH TURNS ROUND. 45 

RECITATION FOR LESSON VII. 
When We see the sun rise in the east, pass through 
the heavens over our heads, and set in the west 
how does it appear to us ? 

As if the earth stood still, and the sun 
moved every day around it. 

How do the moon and the stars appear to move? 

In the same way, in circles or rounded paths 
round the earth. 
What are these movements called ? 

The apparent movements of the heavenly 
bodies, because they really appear to move 
thus round the earth. 

How can these apparent movements be explained ? 

In two ways : first, by saying that the earth 
stands still, while the sun and the stars move 
round it ; second, by saying that the earth 
itself turns round. 
Which is the true way? 

We know that the sun and the stars do not 
really move round the earth ; therefore the 
earth must turn round. 
In what way must the earth turn round to cause the 

apparent movements of the heavenly bodies ? 

From west to east, or the opposite way 
from which they appear to move. 

How will this explain the apparent movements of the 
heavenly bodies? 

As the eastern edge of the earth goes down 



46 YOUNG FOLKS' ASTRONOMY. 

as it turns around, the other heavenly bodies 
come into sight above it, and as the earth 
keeps on moving they appear to cross the 
heavens above our heads until the western 
edge shuts them out of sight. 



LESSON VIII. 

THE EARTH TURNS ROUND ONCE A DAY. 

The earth, then, is all the time spinning" 
round like a top, and the sun and the stars 
appear to us to move only because we on the 
earth are moving ourselves, just as the tele- 
graph poles, the fences, and the trees appear 
to move when we are riding past them in the 
cars. 

To form a still clearer idea of the move- 
ment of the earth, let us return again to the 
lamp and orange (which we have used to 
represent the sun and the earth). It will be 
handier to set up the orange in a pin-cushion, 
as shown in the picture (20). Twist the needle 
so as to make the orange turn round slowly in 
the direction from left to right. The orange 
will thus turn round the needle just as a 
wheel turns round on its axle. The straight 
line which the needle makes through the 
centre of the orange we will call the axis 
(Latin, axis, an axle-tree) of the orange, be- 
cause it is the axle or line around which it turns ; 
and the two ends of the axis, or the points 



4 8 



YOUNG FOLKS' ASTRONOMY. 



where the needle goes into and comes out of 
the orange, we will call the poles (Latin, polus, 
the end of an axis). Draw a circle round the 
middle of the orange, at an equal distance 
in every part from the two poles, and call it 
the equator (Latin, cequus, equal), because it 
divides the orange into two equal parts. 
Now let us apply this to the earth. Of 




20. Lamp and Orange. 

course the earth has no real axis, but as it 
always spins round in just the same way, we 
imagine a line for it to turn on, and call it the 
earth's axis. The two points where this 
imaginary line or axis touches the surface of 
the earth we call the poles, the upper one 
being named the North Pole and the lower 
one the South Pole. Nor is there any circle 



EARTH TURNS ROUND ONCE A DAY. 49 

around the earth like that which we have 
drawn round the orange, but we imagine one 
at an equal distance between the North Pole 
and the South Pole, and call it the Equator, 
because it divides the earth into two equal 
parts. As the whole earth is a sphere (Greek, 



NORTH P01E 




SOUTH POLE 
21. The Earth — its Axis, Poles, and Equator. 

sphaird) or globe, we call the upper half, or 
part between the Equator and the North Pole, 
the Northern Hemisphere (half-sphere), and 
the lower half, or part between the Equator 
and the South Pole, the Southern Hemisphere. 
To go back to the orange again : set a lamp 
in the middle of the table to represent the 



50 YOUNG FOLKS' ASTRONOMY. 

sun, and place the orange and cushion on one 
side of it. It will be seen that while the side 
of the orange toward the lamp is lighted up, 
the other side is in shadow. Stick a pin into 
the middle of the light side and turn the 
orange slowly round by twisting the needle ; 
the pin head will pass out of the light into 
the shadow, go through the shadow, enter 
the light again, and, by the time that the 
orange has turned completely round once, 
the pin head will have reached the place 
where it started from. 

What do we learn from this? We have 
said that the earth turns round on its axis as 
the orange does round the knitting-needle. 
Now, just as the pin head on the orange 
passes from the light of the lamp into the 
shadow and then into the light again, in only 
one turn of the orange, so a like point on the 
surface of the earth passes out of the light of 
the sun through the darkness, and round into 
the sunlight again in exactly one turn. But we 
know that it takes just twenty-four hours for 
such a point to go from the light round into 
the light again (or rather, as the sun does not 
always rise at the same time, let us say from 
the noon of one day to the noon of another) ; 
therefore we know that it takes" the earth 



EARTH TURN'S ROUND ONCE A DAY. 5 1 

twenty-four hours to turn round. In fact, 
the earth turns on its axis once every day ; 
and as the day is made up of day and night, 
each side of the earth is brought round into 
the sunlight once each day, and is cast into 
shadow once each day. This turning of the 
earth on its axis is called its rotation. 

RECITATION FOR LESSON VIII. 
What is the axis of the earth ? 

The line through the centre of the earth 
around which it turns. 
Is there really such a line through the earth? 

No ; we only imagine one for the earth to 
turn around on. 

What do we call the two points on the surface of the 
earth at the ends of this imaginary line or axis ? 

The poles of the earth. 

What are the names of the two poles ? 

The upper one is named the North Pole, 
and the lower one the South Pole. 

What is the Equator? 

A line drawn round the middle of the earth 
at equal distances from the two poles. 

Is there really such a line round the earth? 

No ; we only imagine one to divide the 
earth into two equal parts. 



52 YOUNG FOLKS' ASTRONOMY. 

What are these two parts called? 

The upper half, or part between the 
Equator and the North Pole, is called the 
Northern Hemisphere ; and the lower one, 
or part between the Equator and the South 
Pole, the Southern Hemisphere. 

How fast does the earth turn round on its axis? 

It goes round once every twenty -four 
hours 

What is this movement of the earth called ? 
Its rotation. 



LESSON IX. 

THE TURNING OF THE EARTH CAUSES DAY 
AND NIGHT. 

The earth, then, turns round on its axis once 
in every twenty-four hours, while the sun is 
all the time shining steadily in the heavens ; 
and it is this rotation which causes the differ- 
ence between light and darkness on the earth, 
which we commonly call day and night. If 
the earth did not move at all, one-half of it — 
the side toward the sun — would always be 
flooded with light, while the side furthest 
from the sun would always be in darkness. 
It would therefore be continual day on one 
side and continual night on the other. But 
as it does turn round on its axis, it makes the 
changes of day and night, it being day on our 
side of the earth when it is night on the other, 
and night on our side when it is day on the 
other. 

We can now understand the real meaning 
of morning, noon, and night, of daybreak and 
twilight, of sunrise and sunset. Suppose that 
we are standing at some point on the earth's 



54 YOUNG FOLKS' ASTRONOMY. 

surface — at Washington, for instance — and 
that it is nearly daybreak. As the earth is 
turning round on its axis all the time from 
west to east, its eastern edge is going down 
and bringing into view new parts of the 




22. The Earth in the Heavens lighted on one side by the Sun. < 

heavens, while its rising western edge is shut- 
ting out little by little the heavens on the other 
side. If the sky is clear we shall soon see a 
faint dusky light, called twilight, in the east, 
and we know that the eastern edge of the 
earth is coming near where the sun shines. 



DA Y AND NIGHT. 5 5 

This is the dawn or daybreak, the first appear- 
ance of the light of day. This light gets 
brighter little by little and by and by we see 
a rosy tint, which, as the edge of the earth 
comes nearer to the sun, grows more and 
more yellow until it becomes of the color of 
fire ; soon the edge of the sun comes into view 
and we call it sunrise. This is the name given 
to the first sight of the sun in ancient times, 
when people thought that the sun really rose 
in the east, moved across the heavens, and set 
in the west, while the earth stood still ; and 
we still keep the same name, though we do 
not understand it to mean what the ancients 
did. 

As the earth turns more and more toward 
the east, the sun appears to rise higher and 
higher, going toward the west until it gets 
over our heads. We then say that it is noon 
or midday, and the time between sunrise and 
noon we call the morning or forenoon. 

After midday the turning or rotation of the 
earth gradually brings its western edge nearer 
and nearer to the sun, which is thus made to 
look as if it moved toward the west ; and by 
and by it appears to us to go down behind the 
western horizon. The time between midday 
and sunset we call afternoon, and after sunset 



56 YOUNG FOLKS' ASTRONOMY. 

we call it evening until night sets in. In most 
of the Southern states the people seldom say 
afternoon, but call it evening after twelve 
o'clock in the day ; but this is not the usage 
in other places. 

After the sun has gone out of sight the sky 
and clouds near the horizon are generally col- 
ored with orange, red, and golden tints much 
like those of morning ; but these gradually 
fade away as the western edge of the earth 
rises higher and higher, until at last only a 
gray dusky twilight is left, like that before 
the dawn. After this comes the night, -and if 
there is no moon, the side of the earth on 
which we are remains in darkness until it 
rolls round into the sunlight once more. 

While we are in darkness the opposite side 
of the earth is in sunshine. When it is mid- 
night at Washington it is midday in the cen- 
tre of China ; and when the sun is rising at 
Washington it is just setting there. 

RECITATION FOR LESSON IX. 

What causes day and night on the earth ? 

The rotation or turning round of the earth. 

How do you explain this ? 

When the side of the earth on which we are 
has rolled round into the light of the sun, it is 



DAY AND NIGHT. $7 

day with us and night on the other side of the 
earth ; and when the earth has rolled round so 
far that the sun cannot shine on our side, it 
is night with us and day on the opposite side 
of the earth. 

What would happen if the earth did not move at all ? 

It would be always day on one side of the 
earth and always night on the other. 

What is the real meaning of sunrise ? 

It means that the earth has turned far 
enough in its rotation to bring the sun into 
view above its eastern edge. 

What is noon or midday ? 

The time when the earth has turned round 
far enough to bring the sun over our heads. 

What is the meaning of sunset ? 

It means that the earth has turned round 
far enough to hide the sun from view below 
its western edge. 
What is twilight ? 

The faint dusky light seen before sunrise 
and after sunset. 



LESSON X. 

THE EARTH MOVES ROUND THE SUN. 

We have thus learned that the earth is all 
the time turning round on its axis, and that it 
is this motion which causes day and night. 
Let us see if this rotation will explain all 
the movements the heavenly bodies appear 
to make. As the earth always turns round in 
the same way, without changing, and as the 
stars are fixed in the heavens, we ought al- 
ways to see the same set of stars at the same 
time — that is, the stars which appear at even- 
ing, at midnight, and at sunrise of to-day 
should appear in exactly the same positions 
at evening, midnight, and sunrise of every 
other day throughout the year. 

But is it true that the stars always look the 
same to us at the same time ? No ; if we 
study the heavens carefully every night we 
shall see that the stars are getting further and 
further toward the west all the time, while 
new ones are coming into view in the east. 
In the course of six months they will have 
become so changed that those which we see 



THE EARTH MOVES ROUND THE SUN 59 

at midnight in summer will be different from 
those which we saw in the heavens at mid- 
night in the winter ; but in six months more 
the same stars first seen will appear again, 
and the heavens will look just as they did a 
year before. 

If we watch the sun also, we shall see that 
it appears to have a slightly different position 
each day in the heavens, being one day at its 
rising near one star and the next day near 
another ; but when a year has passed away 
we shall find it again in about the same posi- 
tion in which we first saw it. 

The ancients explained these apparent 
movements of the sun and the stars by saying 
that they moved in circles round the earth ; 
but we know that they are caused by the 
movement of the earth round the sun, in a 
circle, once every year. The earth, then, has 
two movements : it spins round on its own 
axis once every day, and it rolls round the 
sun, somewhat as a ball would roll round a 
race-track, in a great circle once in about 
every three hundred and sixty-five (365) days, 
or a year. 

It may at first be difficult to understand 
how the earth can have these two motions 
at the same time ; but they are very well 



6o 



YOUNG FOLKS' ASTRONOMY. 



shown by a spinning-top. It spins round 
itself very fast, and at the same time moves 
more slowly round in a circle, thus having 
two movements at once. It is the same with 
the earth : it spins round on its axis three hun- 




23. Showing the apparent movement of the Stars. 

dred and sixty-five times while moving round 
the sun once. 

It is easy now to understand why the stars 
appear to move toward the west a little every 
night, and why the sun appears to change its 
place among the stars. In the picture (23), S 
is the sun, and A B are different positions of 



THE EARTH MOVES ROUND THE SUN. 6 1 

the earth as it moves round the sun. Of 
course, it is day on the light side of the earth 
toward the sun, and night on the dark side 
furthest from the sun. When the earth is at 
A, a person on the dark side will see at mid- 
night the stars opposite to the sun. As the 
earth moves onward in its path round the 
sun, the stars will appear to move, little by 
little, in the other direction, until, when it 
gets to B, on the other side of the sun, which 
will be in just six months, an entirely new set 
of stars will light the heavens ; and in six 
months more, when the earth gets round to 
A again, the stars first seen will again come 
into view. 

In the next picture (24) is shown the apparent 
movement of the sun in the heavens, caused 
by the real movement of the earth round the 
sun. When the earth is at the point marked 
1, a person on the light side, or side toward 
the sun, will see the sun in the direction of 
the star A ; but when the earth gets to the 
point marked 2, the sun will appear to be in 
the direction of the star B ; when at 3, in the 
direction of C ; and so on all round the heav- 
ens, the sun appearing in a different place 
among the stars each day. If you walk around 
the lamp, and suppose the objects on the wall 



62 



YOUNG FOLKS' ASTRONOMY. 



to be stars, you will see how the lamp ap- 
pears against different ones from different 
positions. It is just this way that the sun 
appears against different stars as we go round 
it with the earth. 

The great pathway in which the earth 
travels round the sun is called the orbit of 



"X 




24. Showing the apparent movement of the Sun. 

the earth, the word orbit being made from a 
Latin word meaning a circle. Of course, 
there is no real path through the heavens, 
but as the earth always moves in about the 
same line round the sun, we imagine such a 
pathway. We are accustomed to call this 



THE EARTH MOVES ROUND THE SUN. 63 

orbit* a circle, but it is not exactly a circle ; for 
' it is a little longer than it is wide, being thus 
a kind of oval, which we call an ellipse. The 
sun is not exactly in the centre of the earth's 
orbit, but a little nearer one end than the 
other. 

This annual movement of the earth in its 
orbit is called the revolution of the earth 
around the sun. 

RECITATION FOR LESSON X. 

Does the rotation of the earth on its axis explain all 
the movements of the heavenly bodies ? 

No ; if the earth always turned round in 
one place, without changing, the stars seen on 
any night would appear the same on ■ every 
other night of the year. 

Do they always appear the same ? 

No ; they are continually changing, so that 
the stars seen in winter are somewhat different 
from those seen in summer. 

But are not the stars seen in one summer the same as 
those seen in another summer? 

Yes ; when summer comes round again, the 
same stars are again seen. 

Does the sun ever appear to change its place in the 
heavens ? 

Yes ; it appears to change its place a little 
every day, but when the year has passed, it is 



64 YOUNG FOLKS' ASTRONOMY. 

again in the same position in which it was first 
seen. 

What is the cause of these apparent motions of the 
stars and the sun ? 

They are caused by the movement of the 
earth around the sun once every year. 

Has the earth, then, two movements ? 

Yes ; while turning on its axis it is all the 
while rolling in a great circle round the sun. 

What is this circle called? 

The orbit of the earth. 

What is the movement of the earth in its orbit called ? 

The earth's revolution round the sun. 



LESSON XL 

THE EARTHS ORBIT 

The last chapter teaches us that the earth 
has two motions ; one, a spinning motion, in 
which it turns round on its axis once in 
twenty-four hours, or a day ; the other, a 
forward motion, in which it moves in its orbit 
round the sun once in three hundred and 
sixty-five days, or a year. We have also 
learned that the first movement makes our 
day and the changes of day and night; we 
have now to find out what is caused by the 
second movement. 

To do this we must first learn a little more 
about the orbit of the earth. The distance 
of the earth from the sun is so immense that 
it is almost impossible for us to form any idea 
of it. Astronomers tell us that it is about 
ninety-two million (92,000,000) miles, but this 
long row of figures means very little for us. 
Perhaps we may form some idea of it when 
we think that it is three thousand six hundred 
and eighty (3,680) times the distance round 
the earth. We have learned before that it 



66 



YOUNG FOLKS' ASTRONOMY. 



takes about three months, traveling on steam- 
ships and railway cars, to go round the earth ; 
if we should travel at the same rate toward 
the sun, it would take us nearly a thousand 
(920) years to reach it. 

It will be seen by the picture (25) that the dis- 
tance of the earth from the sun at any point 




25. Earth's orbit, ABCE; diameter of orbit, EB; Sun, S. 

in its orbit is only half that of the diameter 
or breadth of the orbit — that is, the distance 
from E to S is half that from E to B ; the 
orbit of the earth must be therefore one 
hundred and eighty-four million (184,000,000) 
miles wide. Now, the circumference of the 
orbit — that is, its length or measure round it 
— is more than three times as much as its 



THE EARTH'S ORBIT. 6j 

diameter, or five hundred and seventy-seven 
million (577,000,000) miles. But great as is 
this distance — so great that our minds can 
scarcely take it in — the earth travels over it 
every year. To do this, it has to move nearly 
eleven hundred (1,097) miles every minute, 
which is more than a thousand times faster 
than the speed of the swiftest railway train. 

It may be hard to understand how the earth 
can travel at this great speed through the 
heavens without our feeling any motion, — 
indeed, almost without our knowing it ; but 
we must remember that we and everything 
else on the earth, even the air around it, are 
borne along at the same speed. Sometimes, 
when we are riding on the railway, the car 
moves so smoothly that we do not feel that 
we are going at all, and it is only when we 
look out of the window and see the trees, 
fences, and other things outside appear to go 
very rapidly in the other direction that we 
become conscious that we are traveling very 
fast. So the motion of the earth, though very 
fast, is so very smooth that we do not feel it, 
and only know it by seeing the sun and the 
stars move the other way. 

In traveling round its orbit the earth moves 
always at the same speed, always smoothly, 



63 YOUNG FOLKS' ASTRONOMY. 

and always keeps in the same plane — that is, 
at the same level, just as a horse does in run- 
ning round a very smooth, flat race-course. 
Imagine a great sheet of pasteboard to be 
spread out flat from the centre of the sun all 
round to the earth's orbit, so as to make an 
immense level surface, and call it the plane 
of the earth's orbit ; this plane is the earth's 
race-course, for it is in it that the earth always 
travels in its yearly journey round the sun. 

Let us now go back once more to the lamp 
and the orange and knitting-needle, shown in 
the picture on page 48. We learned from 
that, by turning the orange round slowly, 
that day and night are caused by the spin- 
ning round of the earth on its axis once every 
twenty-four hours. The axis of the earth is 
there represented as standing straight up and 
down ; if it really stood in this way while the 
earth is going round in its orbit, the equator 
would always be in the plane of the earth's 
orbit, and the two poles of the earth would ' 
always be at the same distance from the sun. 
The rays of the sun would then fall equally 
on both poles, so that the whole half of the 
earth within a line drawn round it through 
each of the poles would be lighted up at once, 
while the other half would be in darkness. 



THE EARTH'S ORBIT. 69 

The days and the nights would then be every- 
where of equal length. But we know that 
they are not of equal length : in our summer 
the days are long and the nights are short, 
and in our winter the nights are long and the 
days are short. 

RECITATION FOR LESSON XI. 
Can you explain the two motions of the earth ? 

It turns round on its axis once every day, 
and rolls round the sun once every year. 

How far is the earth from the sun ? 

About ninety-two million miles. 

How long does it take to go round the earth by rail and 
steamer ? 

About three months. 
How long would it take us to go to the sun if we could 
travel toward it at the same rate of speed ? 

Nearly a thousand years. 

How much longer than the distance from the earth to 
the sun is the earth's orbit ? 

More than six times as long. 

How fast must the earth travel to go over this immense 
distance every year ? 

More than a thousand times faster than the 
speed of the swiftest railway train. 

Why is it that we do not feel any motion when the earth 
is traveling at this great speed through the heavens ? 

Because everything on the earth, even the 



yo YOUNG FOLKS' ASTRONOMY. 

air around it, is borne along at the same rate 
of speed. 

What do you understand by the plane of the earth's 
orbit ? 

The great level field in which the earth 
moves round the sun. 

If the axis of the earth stood straight up and down -while 
it is moving in its orbit around the sun, what would 
happen ? 

The days and the nights would be every- 
where of equal length. 

Are the days and the nights always of equal length ? 

No ; in our summer the days are long and 
the nights short, and in our winter the days 
are short and the nights long. 



LESSON XII. 

WHY THE DA YS AND NIGHTS ARE UNEQUAL. 

How then can we account for the difference 
in the lengths of the days and nights in differ- 
ent seasons ? 

Instead of setting the orange and needle 
straight up in the cushion, as in the picture on 
page 48, set it a little slanting, with the top of 
the needle tipped toward 
the right. In the four 
next pictures (27, 28, 
29, and 30) the orange 
thus slanted is shown on 
four different sides of the 
lamp, the needle being f 
kept at the same slant in ?=r~ 
each position. In the 
first position (27) the 26 ' ° ra ^ l ^f needIe 
lamp being supposed to 

be at the place marked S, the upper end of 
the needle is farther away from the lamp than 
the lower end. If you now turn the orange 
round, by. twisting the needle with your 
fingers you will see that the light does not 




72 



YOUNG FOLKS' ASTRONOMY. 



shine at all on a part round the north pole, 
while it shines all the time round the south 
pole, and that all the parts on the line of the 





27. First Position. N, North Pole; S, South Pole; 
EE, Equator. 

equator are lightened and darkened equally. 
If the earth were always in this position 
toward the sun, it would be always night at 





28. Second Position. 



the north pole, and always day at the south 
pole. 

Stick a pin in the orange about half way 



DAYS AND NIGHTS UNEQUAL. 73 

between the equator and the north pole. As 
the orange turns round you will see that the 
pin has a longer course to travel on the dark 
side than on the light side. In these parts, 
therefore, the nights are longer than the 
days. But if you stick the pin half way be- 
tween the equator and the south pole, it will 
be much longer in the light than in the 
shadow in passing round the orange ; the 
days, therefore, in these parts are longer than 
the nights when the earth is in this position. 

Move the orange one quarter round the 
table, as in the next picture (28). You will 
see, although the needle is kept at the same 
slant as before, that the poles are now at the 
same distance from the lamp, and that the 
light shines equally on them. When the earth 
is in this position one half of it is in the sun- 
light, while the other half is in shade, and the 
days and nights are therefore equal every- 
where. 

Move the orange another quarter round 
the table, as in the third position (29). The 
north pole will now be nearer the lamp than 
the south pole, and the light will shine all the 
time round the north pole, while the south 
pole will be in shadow. When the earth is in 
this position, therefore, it will be always day 



YOUNG FOLKS' ASTRONOMY. 



at the north pole and always night at the 
south pole. The pin between the equator 
and the north pole' will now be longer inpass- 





# 29. Third Position. 

ing through the light side than through the 
dark side, and in the same parts on the earth 
the days will be longer than the nights. 





30. Fourth Position. 

Lastly, move the orange round another 
quarter ; it will then be in the position shown 
in the fourth picture (30). The poles will 



DAYS AND NIGHTS UNEQUAL. 7$ 

now be again at equal distances from the 
lamp, so that the light will shine on both at 
the same time. When the earth is in this 
position, one half is again in the sunlight, 
while the other half is in the shadow; the 
days and nights, therefore, are everywhere 
equal. 

It must not be thought, because we have 
shown four positions of the earth in its jour- 
ney around the sun by placing the orange on 
four sides of th.e lamp, that the earth passes 
at once from one to another of these positions 
in traveling round its orbit; it moves from 
one to another gradually, passing through 
many other positions as it goes, so that the 
days and the nights lengthen and shorten 
little by little. Some of these other positions 
can be seen in the next picture (31), where the 
earth is shown at different places in its orbit. 
Of course in this picture the earth is drawn 
very much larger in proportion to the sun 
than it really is, because if it were made of its 
proper size it would be so small that we could 
scarcely see it. The axis of the earth, too, is 
made to extend from the poles, as the knitting 
needle does from the poles of the orange, so 
as to show the slant of the axis to the plane 
of the earth's orbit. 



7 6 



YOUNG FOLKS' ASTRONOMY. 



When the earth is at A (position 2 of 
orange), its axis, though slanting in one way, 
does not slant toward the sun, but is in all its 
parts at the same distance from it, so that it is 
shone upon just as if it stood straight up and 
down. Both poles are therefore touched by 
the sunlight, and night and day are equal in 
all parts of the earth. In passing from A to 




31 Different Positions of the earth in its journey round the 
Sun. 



B the north pole of the axis gradually gets 
nearer to the sun, while its south pole gets 
farther from it ; and during all this time the 
north pole is in the light, while the south pole 
is in the dark : it is, therefore, at this time of 
the year always day at the north pole and al- 
ways night at the south pole. On the equator 
the days and nights are of the same length, 
but in the Northern Hemisphere the days are 



DAYS AND NIGHTS UNEQUAL. 77 

longer than the nights, while in the Southern 
Hemisphere the nights are longer than the 
days. In moving from B to C the axis of the 
earth becomes less and less slanting toward 
the sun, until, when it reaches C, the two 
poles are again at equal distances from it, and 
the light just touches both again. During 
this time the north pole has continued in the 
light and the south pole in the dark, but in 
the Northern Hemisphere the days have been 
growing shorter and the nights longer, and 
in the Southern Hemisphere the nights have 
been growing shorter and the days longer, 
until at C both are again of equal length. 

We thus see that it has been day at the 
north pole and night at the south pole during 
all the time in which the earth has been mov- 
ing from A through B around to C. The 
day has therefore continued for six months at 
the north pole, and the night for six months 
at the south pole : at the equator the days and 
nights have all been of the same length, but 
at most places in the Northern Hemisphere 
the days have all been longer than the nights, 
and it has been summer, while at most places 
in the Southern Hemisphere the nights have 
all been longer than the days, and it has been 
winter. 



78 YOUNG FOLKS' ASTRONOMY. 

While the earth is passing from C to D the 
north pole of its axis is gradually getting far- 
ther away from the sun, and the south pole 
nearer to it : the night is therefore just begin- 
ning at the north pole, and the day at the 
south pole ; and as the north pole remains in 
shadow while the earth is moving round 
through D to A again, it follows that during 
all this time (six months) it is night and win- 
ter at the north pole, and day and summer at 
the south pole : at the equator the days and 
the nights have all been of the same length, 
but at most places in the Northern Hemi- 
sphere the nights have all been longer than 
the days, and it has been winter; while at 
most places in the Southern Hemisphere the 
days have all been longer than the nights, and 
it has been summer. 

RECITATION FOR LESSON XII. 
How does the axis of the earth stand in the plane of its 
orbit ? 

It slants a little toward the plane of its orbit. 

Does it always keep in this position ? 

Yes ; it always keeps the same slant while 
the earth rolls around the sun. 

What is caused by this slanting of the earth's axis ? 

The days and nights are made of unequal 
length. 



DA YS AND NIGHTS UNEQUAL. 79 

Why is this ? 

Because some parts of the earth are thus 
kept longer in the sunlight, while others are 
kept longer in the shadow. 

How is it with the parts around the equator ? 

They are always equally in sunshine and in 
shadow, and the days and nights there are 
therefore always of equal length. 

How long are the days and nights at the two poles ? 

Always six months each ; and it is always 
day at the north pole when it is night at the 
south pole. 

Are the two poles ever equally distant from the sun ? 

Yes ; at two points in the earth's journey 
around the sun the poles are equally distant 
from it, and the days and nights are then equal 
all over the earth. 

When it is night at the north pole, what is the difference 
between the days and nights in most other parts of the 
Northern Hemisphere ? 

The nights are longer than the days. 

When it is day at the north pole, what is the difference 
between the days and nights in most other parts of the 
Northern Hemisphere? 

The days are longer than the nights. 



LESSON XIII. ■ 

THE CHANGES OF THE SEASONS. 

Now, what have we learned in the last 
chapter ? 

First, that although the turning of the earth 
on its axis makes day and night, the difference 
in the length of the days and the nights is 
caused by the yearly movement of the earth 
round the sun and by the slant of its axis to 
the plane of its orbit. 

Second, that there are two points in the 
earth's journey in its orbit round the sun 
where the slant of its axis makes no difference 
in the length of the days and nights, because 
its two poles are then at the same distance 
from the sun. 

Third, that the days and nights are always 
of equal length on the line of the equator, in 
whatever position the earth may be in its 
orbit. 

Fourth, that it is always day at the north 
pole and night at the south pole during the 
six months of the year when the north pole of 
the earth's axis is the nearer to the sun, and 



THE CHANGES OF THE SEASONS. 8 1 

always night at the north pole and day at the 
south pole during the six months when the 
south pole of the earth's axis is the nearer to 
the sun. 

Fifth, that at places between the equator 
and the poles the days and the nights are of 
unequal lengths whenever either of the poles 
is tipped toward the sun. 

If you clearly understand these things, you 
can also understand how this difference be- 
tween the length of the days and nights causes 
the changes of the seasons — spring, summer, 
autumn, and winter. Heat, like light, comes 
from the sun, and it is when we have the most 
light (in the day-time) that the earth becomes 
heated, and when there is the least light (in 
the night-time) that it becomes cooled. It 
becomes most heated then when the days are 
longest, and most cooled when they are short- 
est ; and summer is the season of long days 
and winter the season of long nights, while 
spring and autumn are the seasons when the 
days and the nights are more nearly equal in 
length. 

In the Northern Hemisphere, in which we 
live, the nights are longest in December; the 
earth there has less of the sun than at any 
other time of the year, and therefore becomes 



82 YOUNG FOLKS' ASTRONOMY. 

most cooled, and we call it winter. After 
that the days begin to grow a little longer, 
and the earth to get more sun, until in March 
the days and the nights become equal in 
length, and we call it spring. From this time 
the days grow longer little by little, so that 
the earth gets more light and heat, until June, 
the season of the longest days and the shortest 
nights, when we call it summer. From sum- 
mer the days grow shorter and shorter until 
they become of the same length again with 
the nights, in September, when we call it 
autumn, and the nights then grow longer 
than the days until winter comes round again 
in December. 

We have learned that when the nights are 
longest in the Northern Hemisphere the days 
are longest in the Southern Hemisphere ; 
therefore when it is winter here it must be 
summer there. This will be understood more 
easily by looking at the picture on page 76. 
When the earth is at the point in its orbit 
marked D (about December 21), the south 
pole is nearest the sun : it is therefore summer 
in the Southern Hemisphere because the days 
are long and the nights are short, and winter 
in the Northern Hemisphere because the 
nights are long and the days are short. Win- 



THE CHANGES OF THE SEASONS. 83 

ter continues in the Northern Hemisphere for 
three months while the earth is moving round 
toward the point marked A. When A is 
reached (about March 21) the days and nights 
are equal, and it is spring in the Northern 
Hemisphere and autumn in the Southern 
Hemisphere. Spring continues in the Nor- 
thern Hemisphere for three months while the 
earth is moving round to B. When it reaches 
B (about June 21), the north pole is nearest 
the sun : it is therefore summer in the North- 
ern Hemisphere, because the days are long 
and the nights are short, and winter in the 
Southern Hemisphere because the nights are 
long and the days are short. Summer con- 
tinues in the Northern Hemisphere for three 
months while the earth is moving round to- 
ward C. When it reaches C (about Septem- 
ber 21), the days and nights are again equal, 
and it is autumn in the Northern Hemisphere 
and spring in the Southern Hemisphere. 
Autumn then continues three months in the 
Northern Hemisphere, until the earth reaches 
D, when winter again begins. 

The positions of the earth in its orbit 
marked A and C in the picture on page 76 
are called the equinoxes — that is, the times of 
equal nights (and days), (Latin ceqiius, equal, 



84 YOUNG FOLKS' ASTRONOMY. 

and 7iox, night), A being- with us the vernal 
(spring) equinox, because it is then spring in 
the Northern Hemisphere, and C the au- 
tumnal equinox, because it is then our autumn. 
The other two positions of the earth, B and 
D, are called the solstices (Latin solstitinm, 
from sol, the sun, and sistare, to stand still), 
that is, the standing still of the sun, because 
the sun then appears to stand still for a few 
days ; B being in the Northern Hemisphere 
the summer solstice and D the winter sol- 
stice. 

RECITATION FOR LESSON XIII. 

What is caused by the difference in the length of the 
days and the nights? 

The changes of the seasons — spring, sum- 
mer, autumn, and winter. 

How do you explain this ? 

Heat as well as light comes from the sun ; 
when the days are longest therefore the earth 
becomes most heated, and we then have sum- 
mer; and when the nights are longest the 
earth becomes most cooled, and we then have 
winter. 

What then are spring and autumn? 

The seasons when the days and the nights 
are nearly equal in length. 



THE CHANGES OF THE SEASONS. 85 
When does winter begin in the Northern Hemisphere? 

In December, because then the nights are 
longer than the days. 
About what time are the nights longest? 

About December 21. 

Do they continue of the same length ? 

No ; they grow a little shorter every day 
until March 21, when they are of about equal 
length with the days, and we then call it 
spring. 
Do they remain long of equal length? 

No; the days then grow a little longer 
until about June 21, when they reac^i their 
greatest length, and we call it summer. They 
then grow shorter all the while till Septem- 
ber 21, when the days and nights are again of 
equal length, and we call it autumn. 

How long do the nights then grow longer? 

Until December, when winter comes round 
again. 
When it is winter in the Northern Hemisphere, is it 

also winter in the Southern Hemisphere? 

No ; when it is winter here, it is summer 
there, and when it is spring here, it is autumn 
there. 



LESSON XIV. 

CLIMATE AND THE ZONES OF THE EARTH. 

We have thus learned that the four seasons 
— spring, summer, autumn, and winter — are 
caused by the difference in the lengths of the 
days and nights, and that the seasons differ 
on opposite sides of the earth because when 
the days are long and the nights are short on 
one sifle, the nights are long and the days 
are short on the other. It is now easy to 
understand why it is winter in China when it 
is summer in the United States, and summer 
there when it is winter here; but we must 
not make the mistake of thinking that seasons 
like ours are found all over the world, for 
they belong only to those parts of the earth 
called the temperate zones. 

We shall understand this better if we first 
learn something about climate. The sun 
does not shine alike on all parts of the earth ; 
some parts therefore get much more heat 
than others, and thus it follows that while 
some countries have a warm climate, others 
have a cold climate. Let us set up the orange 



CLIMATE AND ZONES. 87 

and knitting-needle once more in front of the 
lamp ; we shall see that the light falls straight 
upon the middle part of the orange, that is, 
on the part around the equator, that it falls 
slanting on the parts half way between the 
equator and each of the poles, and still more 
slanting on the parts near the poles. It is 
the same with the earth ; all its parts are 
warmed and lighted by the sun as it turns 
round, but not all equally ; the parts around 
the equator get the direct heat of the sun's 
rays, as we do at noon, and are therefore the 
warmest parts of its surface, the heat lasting 
all the year round ; while those at the poles 
get the rays very slanting, as we do at even- 
ing, and are therefore the coldest parts of the 
earth — the regions of everlasting snow and 
ice. Between these two are more temperate 
climates, where the heat and the cold are 
about equal, and where only the seasons 
change four times each year. 

We thus divide the surface of the earth 
into several zones or belts, as shown in the 
picture (32), by drawing round it circles paral- 
lel to — that is, running the same way with — 
the equator. The two circles nearest the equa- 
tor, one above and one below it, are called 
the tropics, the northern one being called the 



88 



YOUNG FOLKS' ASTRONOMY. 



Tropic of Cancer, and the southern one the 
Tropic of Capricorn ; the zone or belt be- 
tween these circles is called the Torrid Zone, 
that is, the hot zone, because it is the place 
of the greatest heat. The sun shines directly 
' upon it all the days of the year, so that it is 



NOHTH POLE 




SOUTH POLE 

32. The Circles of the Earth. 

hot continually, and has no change of seasons 
like ours. 

The Polar Circles are circles drawn round 
each of the poles, at a certain distance from 
them. The one round the north pole is called 
the Arctic Circle, and the one round the 
south pole the Antarctic Circle. The zone 



CLIMATE AND ZONES. 5Q. 

between the Arctic Circle and the north pole 
is called the North Frigid or cold Zone, and 
the one between the Antarctic Circle and the 
south pole the South Frigid Zone. As the 
sun shines upon these zones during only a 
part of the year, and with very slanting rays, 
they are the coldest parts of the earth. They 
have not four seasons like ours, but winter 



NORTH POLE. 



NORTH POLE. 




SOUTH POLE. SOUTH POLE. 

33. The Zones of the Earth. 

lasts through nearly half the year, and sum- 
mer through nearly the other half; but the 
sun's rays give but little heat, and the summer 
is scarcely warm enough to melt the snow. 
At the poles themselves the day lasts for six 
months, and is followed by a night of six 
months, so that the polar day and year are 
the same. 



90 YOUNG FOLKS' ASTRONOMY. 

Between the tropics and the polar circles 
lie the temperate zones, or zones of moderate 
heat ; the one between the Tropic of Cancer 
and the Arctic Circle being called the North 
Temperate Zone, and the one between the 
Tropic of Capricorn and the Antarctic Circle 
being called the South Temperate Zone. In . 
these two zones the rays of the sun do not 
fall upon the earth so straight as they do in 
the torrid zone, and the heat is not so great 
as it is there ; they also fall upon it less slant- 
ing than in the polar circles, and the cold is 
not so intense as there ; their climate there- 
fore is much more moderate than that of 
either of the other zones, and much better 
fitted for mankind ; and it is only in them 
that regular changes in heat and cold enable 
us to divide the year into four seasons. 

It must be borne in mind that these circles, 
by which we divide the surface of the earth 
into zones, are, like the equator, only imagi- 
nary lines, and that there are really no such' 
divisions. It must also be clearly understood 
that the climate is not exactly the same in all 
parts of each of the zones ; in the torrid 
zone, for instance, it is hotter near the equa- 
tor than in the parts near the temperate zones, 
and that in either of the temperate zones the 



CLIMATE AND ZONES. 9 1 

parts near the torrid zone are warmer, and 
the parts near the polar circles cooler than 
the middle parts. There are also other differ- 
ences that cannot be explained here. 

RECITATION FOR LESSON XIV. 
Are seasons like ours found all over the earth ? 

No ; they belong only to those parts of the 
earth called the temperate zones. 

Does the sun shine alike on all parts of the earth ? 

No ; its rays fall straight on the parts 
around the equator, and they therefore get 
its full heat and are the warmest parts on the 
earth's surface ; but they fall very slanting on 
the parts around the poles, and those parts 
therefore get little heat and are the coldest 
parts on the earth's surface. 

Are there not parts on the earth's surface where the 
heat and the cold are nearly equal ? 

Yes ; the parts between the equator and 
the poles. 

What are these differences in the heat of different 
parts of the earth called ? 

Climate. 

How is the earth divided according to climate ? 

Into five zones or belts: the zone around 
the equator is called the Torrid Zone ; that 
around the North Pole the North Frigid 



92 YOUNG FOLKS' ASTRONOMY, 

Zone, and that between this and the Torrid 
Zone the North Temperate Zone ; the zone 
around the South Pole is the South Frigid 
Zone, and that between it and the Torrid 
Zone the South Temperate Zone. 

Is the climate in all parts of each of these zones ex- 
actly alike? 

No ; in the torrid zone the parts near the 
equator are much hotter than those near the 
temperate zones ; and in the temperate zones 
the parts near the torrid zone are warmer 
and those near the frigid zones are cooler 
than the middle parts. 



LESSON XV. 

THE SUN. 

We have now learned that the earth is a 
globe which moves round the sun once every 
three hundred and sixty-five (365) days, and 
that it is this movement which makes our 
year ; that it also spins round on its own axis 
once in twenty-four (24) hours, thus making 
our day, and that the division of the day into 
day and night on any part of the earth is 
caused by that part's coming into and going 
out of the sunlight. We have also seen that 
the difference in the length of the days and 
nights is caused by the slanting of the earth's 
axis, so that the sun shines longer on some 
parts than on others, and that this causes 
climate and the changes of the seasons. 

Thus from the sun comes our heat and 
light. Without it the earth would be an icy 
desert, covered with eternal darkness, wholly 
unfit for the growth of plants and animals, 
and unsuited for the abode of man. What 
then is this sun, on which depends the very 
life of everything on our earth ? 



94 YOUNG FOLKS' ASTRONOMY. 

It is dangerous to look at the sun when it 
is shining brightly, either with the eye alone 
or through a telescope, as one may easily be 
blinded by it ; but it may be looked at safely 
through a piece of glass smoked over a 
candle. It appears, when seen in this way, 
like a round bright object, and not very 
large — not much larger, indeed, than the full 
moon commonly looks ; but we would make 
a mistake if we should judge of its size from 
its appearance alone, for the further away 
any object is, the smaller it looks to us. We 
have already learned (Lesson X.) that the sun 
is distant from the earth about ninety-two 
million (92,000,000) miles ; it must then be of 
immense size to look even as large as it does 
from such a distance. 

The earth, around which it takes us three 
months to travel by means of railways and 
steamships, seems very large to us ; but if we 
should make one and a quarter millions of 
globes as large as it into one great ball, it 
would not be as large as the sun. Indeed, 
compared with the great sun, our earth is a 
very small thing in the universe. 

When viewed with the eye alone the sun 
appears to be of nearly the same brightness 
in all parts, but when viewed through a tele- 



THE SUN. 95 

scope it is seen to be brighter in the centre 
than in the outer parts. Its surface has a 
mottled or blotchy appearance, as if strewn all 
over with something shaped like little grains, as 
shown in the picture (34), which is made from 




34. Photograph of the Sun. [Newcomb and Holden's 
Astronomy.] 

a photograph. Dark patches or spots are 
also seen on parts of its surface, sometimes 
singly and sometimes in groups, some of 
them small and some so large that several 
globes of the size of our earth would not 
cover one of them. When looked at through 



g& YOUNG FOLKS' ASTRONOMY. 

a very large telescope, these spots are seen to 
be not merely patches on the surface of the 
sun, but deep holes in it. They generally 
look darkish in the middle, with a ragged 
fringe or border of a lighter color, much like 
that shown in the picture (35). By carefully 




Sun Spot. [Newcomb and Holden's Astronomy.] 



watching these spots, they have been found 
to move slowly from the east side of the sun's 
face toward the west side. After going out 
of sight on the west side, they have been seen 
to appear again on the east side, and to pass 
across the sun's face as before, going thus 



THE SUN. 97 

entirely round it in about twenty-five days. 
It is supposed from this that the sun is all 
the time moving round and carrying these 
spots with it, and that it therefore turns on 
its axis as the earth does, but much more 
slowly than the earth, going round only once 
in about twenty -five or twenty-six days. 

When the sun is hidden from us by the 
moon in a total eclipse, as told about in Lesson 
XVIII., it presents a far grander appearance 
than it usually does. As soon as its face is 
hidden by the moon, a beautiful silvery or 
pearly light is seen glowing all round the globe 
of the moon, brightest next to the moon, and 
shading off little by little toward the outer 
edge. This is called the corona (Latin for 
crown), because it looks much like a crown 
of light. It is not always round, but is some- 
times more nearly square, and sometimes has 
points like rays of light extending from it, as 
shown in the picture. Besides the corona, 
jets of reddish flame are seen to shoot out at 
different places around the moon's disk, like 
great tongues of fire. It was once thought 
by many that the corona and the jets of flame 
belonged to the moon, but it is now known 
that they are parts of the sun. We cannot 
tell exactly what causes the corona, but the 




36. Corona of the Sun during the Eclipse of July 29, 187 
[Newcomb and Holden's Astronomy.] 



THE SUN. 99 

flame jets are supposed to be masses of burn- 
ing gas which shoot up from a layer of burn- 
ing gases by which the surface of the sun is 
surrounded. This layer is called the chromo- 
sphere or color sphere (Greek, chroma, color, 
and sphaira, sphere), because it colors in some 
degree the light of the sun. It cannot be seen 
with the naked eye, and seldom through a tele- 
scope. The chromosphere is made up chiefly 
of hydrogen gas, and is thought to be much 
like an ocean of fire, which is always in mo- 
tion, like flames blown by the wind, and from 
which the fiercely blazing vapors frequently 
spout up hundreds of thousands of miles. 

Under the chromosphere is the surface of 
the sun, which is the only part commonly 
seen. This, which looks to us like a shining 
globe, is called by astronomers the photo- 
sphere or light sphere (Greek phos, light, and 
sphaira, sphere), because from it comes the 
light of the sun. We do not know exactly 
how the great globe of the sun is made, but 
the best astronomers now think that the surface 
or photosphere is a solid or nearly solid crust, 
and that its inside is made up of gases packed 
very closely together, but which are kept 
from becoming liquid by the heat. This 
heat is so great that we have nothing on the 



I CO YOUNG FOLKS' ASTRONOMY. 

earth to compare it with, metals and other 
minerals being turned into vapor by it as 
easily as water is turned into steam here. 
We know this by examining the light of the 
sun with the spectroscope, which shows that 
it is made up not only of burning hydrogen 
and oxygen, but also of the gases of iron, 
zinc, copper, nickel, cobalt, "aluminum, sodium, 
magnesium, calcium, and other metals. 

The sun, then, is an immense globe, made up 
mostly of highly heated gaseous matter, turn- 
ing on its axis in the heavens, and giving off 
light and heat to all around it. The earth is 
at such an immense distance from it that it 
gets but very little of this light and heat, but 
even this little is often strong enough to be 
very uncomfortable. If we were much nearer 
to the sun, we would be blinded and scorched 
by its rays; and if we were much farther 
from it, we would have neither light nor heat 
enough for our comfort. 

RECITATION FOR LESSON XV. 
From whence comes our light and heat ? 

From the sun. 

How large does the sun look when seen through smoked 
glass ? 

About as large as the full moon. 



THE SUN. IOI 

Can we judge of its size in this way ? 

No ; because it is a great distance from us; 
and the farther a thing is away the smaller it 
looks. 

How large is the sun compared with the earth ? 

It is more than one and a quarter million, 
times as large as -the earth. t 

How does the sun look through a telescope ? 

It looks brighter in the centre than in the 
outer parts, and appears to be strewn over 
with something like little grains. 

What else can be seen ? 

Dark patches or spots, which are seen, when 
viewed through a very large telescope, to be 
holes in its surface. 

How do these spots appear to move on the sun ? 

They appear to move across from the east 
to the west side, then go out of sight, and in 
time to come again on the east side and move 
across the sun's face as before. 

How long does it take the spots to thus go round the 
sun? 

About twenty-five days. 

What do we conclude from this ? 

That the sun turns round on its axis once 
in about twenty-five days, carrying the spots 
with it. 



102 YOUNG FOLKS' ASTRONOMY. 

What is seen when the sun's face is hidden by the moon 
in a total eclipse ? 

A crown of silvery light, called the corona, 
is seen all around the moon, and jets of red- 
dish flame shoot out like tongues of fire. 

What causes these appearances ? 

They come from the sun. We do not know 
exactly what causes the corona, but the flame 
jets are supposed to be burning gases which 
shoot up from the sun. 

With -what is the sun supposed to be covered ? 

With a layer of burning gases much like an 
ocean of fire, which is always in motion, and 
from which fiercely blazing vapors spout up 
hundreds of thousands of miles high. 

What is this gaseous layer called ? 

The chromosphere. 

What is the photosphere ? 

The surface of the great globe of the sun, 
which lies under the chromosphere. 

Which is the part commonly seen ? 

The photosphere ; the corona and the chro- 
mosphere can be seen only when the sun is 
hidden by the moon. 

How do the best astronomers now think that the globe of 
the sun is made up ? 

They think that the photosphere is a solid 
or nearly solid crust, and that the inside of 



THE SUX. I03 

the sun is made up of gases packed very 
closely together. 

Do we know what any of these gases are ? 

Yes ; by examining the light of the sun, it 
has been found to consist of burning hydro- 
gen and oxygen, and of the gases of many 
metals. 

Do these burning gases give out great heat ? 

Yes ; so great that if the earth were much 
nearer the sun, we should be blinded and 
scorched by its rays. 



LESSON XVI. 

THE MOON AND ITS PHASES. 

We have learned that the sun gives us light 
and heat. But, one may say, the moon gives 
us light by night ; how then do we get all our 
light from the sun ? It is true that we get 
some light from the moon, but it is not its 
own light ; the moon gives no light of its 
own, but only reflects the light of the sun. 

Every object which we see shone upon by 
light reflects or bends some of the rays of 
that light to our eyes, and enables us to see 
the object. Other rays fall on objects around 
us, and are in turn reflected to oifr eyes by 
those objects, so that we are enabled to see 
them also. So, although the moon has no 
light of its own, it reflects to us a part of the 
sun's rays, and these form in our eyes an 
image of the moon which we can see, and 
other rays from the moon falling on objects 
around us are again bent or reflected to our 
eyes so that we can see them also ; and thus 
it is that everything which the moon lights 
on the earth is seen by us. 



THE MOON AXD ITS PHASES. 105 

Why then is it, one may ask, that we do 
not always see the moon alike? The sun is 
always shining in the heavens, but sometimes 
the moon looks large and round to us, and 
sometimes small and narrow like a crescent, 
while at other times we cannot see it at all. 

To understand this well we must first learn 













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37. The Moon and the Earth — comparative size. 



something more about the moon. Like the 
earth, the moon is a globe which floats in the 
heavens. It looks to us to be nearly as large 
as the sun, but it is really much smaller than 
the earth (it would take about fifty balls like 
the moon to make one globe of the size of the 
earth), and looks larger, only because it is near 



106 YOUNG FOLKS' ASTRONOMY. 

to us — that is, near compared with the dis- 
tance of the sun. Its distance from the earth 
is about two hundred and forty thousand 
(240,000) miles, or about ten times the earth's 
circumference. So, if we could use the same 




\ 

V 
\ 

\ 
38. The Moon in its Orbit. 

means of travel, it would take only about ten 
times as long to go to the moon as to go 
around the earth. This seems to us on the 
earth a great distance, but it is really very 
small when we think of the immense size of 
the universe and the distances of the other 



THE MOON AXD ITS PHASES. \OJ 

heavenly bodies, for the moon is much nearer 
to us than any other of them. 

Now, we know, for reasons which cannot 
be explained here, that the moon is all the 




The Moon and its Phases. 



time moving round the earth, while the earth 
is moving- round the sun. The orbit, or path- 
way, of the moon is nearly a circle, and it 
takes it about a month to travel round it 
once. It is shone upon hy the sun during 



108 YOUNG FOLKS' ASTRONOMY. 

this time, but as it is a sphere or globe, only 
the half of it toward the sun is lighted up by 
the sun's rays, while the other half is in 
shadow. Sometimes we on the earth see the 
whole of the light side, sometimes only a part 
of it, and sometimes the dark side is toward 
us so that none of the sun's rays are reflected 
to us, and then we do not see it at all. 

These different appearances of the light 
part of the moon, as it moves round the earth, 
are called its phases Greek, phasis, appearance. 
We shall understand them better from the 
picture (39), which shows the earth and the 
moon in eight different positions in its orbit 
around it. In this the earth is in the cen- 
ter, and AECGBHDF is the moon in dif- 
ferent places in its orbit, with one-half of 
it lighted up by the sun, supposed to be at a 
very great distance away on the right. The 
outside globes show the way the moon in 
these different positions looks to us on the 
earth. When the moon is at A, between the 
earth and the sun, it is said to be in conjunc- 
tion (Latin, conjanctiim, joined or united), be- 
cause the two appear to be joined together. 
When in conjunction, the light side of the 
moon is turned entirely away from the earth, 
and we cannot see it at all. It is then called 



THE MOON AND ITS PHASES. IO9 

new moon, for the moon is really there al- 
though not visible to us. 

Soon after leaving the position at A, a part 
of the moon on the side toward the sun ; 
begins to be seen, like a narrow crescent, 
with the horns, turned from the sun, as in E. 
The crescent (Latin, crescens, growing, so 
called because it increases in size) grows 
wider as the moon travels on, until at C one- 
half of the lighted part — that is, one-quarter 
of the whole moon — can be seen from the 
earth, and the moon is then said to be in her 
first quarter. 

More and more of the lighted side now be- 
comes visible to us as the moon moves on, 
until at G we see more than half of the lighted 
side, and the moon is said to be gibbous 
(Latin, gibbus, hump-backed) — that is, swelled 
or rounded out. At B, when the moon is on 
the opposite side of the earth from the sun, 
it is said to be in opposition (Latin, oppositum, 
set or placed opposite). The whole of the 
lighted side is then seen, and we call it full 
moon. 

In passing round the other side of her orbit 
the moon shows the same forms, only in the 
backward order ; thus, at H she looks as she 
did at G, and is again called gibbous ; at jD, 



IIO YOUNG FOLKS' ASTRONOMY. 

when she is said to be in her last quarter, she 
presents the same appearance that she did at 
Cy and at F the same that she did at F, until, 
when she reaches A again, she is once more 
invisible to us, and we again have new moon. 
Some of the ancients had singular notions 
about the changes of the moon. The people 
of Hindoostan used to say that the moon was 
full of nectar, which the gods ate little by 
little, and that this was the cause of its grow- 
ing smaller when it waned ; and that the 
nectar grew again when the moon waxed or 
became large again. Some savage nations 
think that the moon breaks up into stars 
when it becomes small, and is made anew 
each month. 

It must not be forgotten that the earth is 
all the time moving round the sun while the 
moon is moving round the earth, and that the 
moon itself is thus always traveling with the 
earth round the sun. It is therefore called 
the satellite (Latin, safeties, an attendant) or 
attendant of the earth, because it follows it 
around as a servant does his master. 

It has been said that it takes the moon 
about a month to travel round the earth once. 
The real time between one new moon and 
the next is about twenty-nine and a half days. 



THE MOON AND ITS PHASES. Ill 

RECITATION FOR LESSON XVI. 
Whence does the moon get its light ? 

From the sun ; the moon has no light of its 
own. 
How are we enabled to see anything? 

Everything we see shone upon by light 
reflects or bends a part of that light to our 
eyes ; and this is what enables us to see the 
thing thus shone upon. 
How does this esplain the moonlight ? 

The sun shines upon the moon, and a part 
of the light which it gets is reflected to us 
so that we are able to see the moon and the 
things on the earth which it lights. 

What is the moon? 

A globe like the earth, but much smaller 
than it. 
Why then does it look nearly as large as the sun ? 

Because it is very near to us, compared 
with the distance of the sun. 

How far is it from the earth? 

About two hundred and forty thousand 
miles. 

How long would it take to go to the moon if we could 
use the same means of travel that we do on the 
earth? 

About ten times as long as it would take 
to travel round the earth. 



112 YOUNG FOLKS' ASTRONOMY. 

What motion has the moon ? 

It revolves in its orbit around the earth, 
just as the earth revolves around the sun. 

Hoot long is it in going round in its orbit? 

About a month. 

Why does not the moon always look the same to us? 

Because only the half of it toward the sun 
is lighted by its rays ; sometimes we see the 
whole of the light side, sometimes only a part 
of it, and sometimes, when the dark side is 
toward us, we do not see it at all. 

What are the different appearances of the moon called ? 

Its phases. 

What are the principal phases of the moon ? 

When the dark side is toward us it is called 
.new moon ; when a quarter of the bright 
side can be seen, it is said to be in its quar- 
ter;^ when three-fourths can be seen, it is 
called gibbous ; and when the whole of its 
lighted side is toward us, it is called full moon. 

When is the moon said to be in conjunction? 

When it is between the earth and the sun. 

What is neOT moon? 

When the light side of the moon is turned 
from us so that we cannot see it at all. 

When is the moon said to be in her first quarter? 

When it first shows, after new moon, one- 
half of its lighted part. 



THE MOOX AND ITS PHASES. 113 

When is the moon called gibbous? 

When more than half of the bright side is 
shown, so that it appears to be rounded or 
swelled out. 

What is full moon? 

When all the bright side is shown to us. 

When is the moon said to be in opposition ? 

When it is on the opposite side of the 
earth from the sun. 

When is the moon said to be in her last quarter? 

When it shows, just before new moon, one- 
half of its lighted part. 

Why is the moon called the earth's satellite ? 

Because it follows the earth around the 
sun as a servant follows his master. 



LESSON XVII. 

WHA T THE MOON IS LIKE. 

If we look with the unaided eye at the 
moon when it is full or nearly full, on a clear 
night, we shall see that some parts of its sur- 
face are darker than others, giving it a mot- 
tled appearance. These spots or blotches 
somewhat resemble the features of a human 
face, and probably gave rise to the story of 
the man in the moon. But when the moon is 
viewed through a telescope this appearance 
changes, and the surface is seen to be made 
up of mountains, valleys, and plains. 

The moon has been studied very carefully 
by astronomers, and we have now good maps 
of its surface, on which the different parts are 
carefully set down and named. The darker > 
patches were thought in former times to be 
seas, and on the maps they are still called 
seas, though they are now known to be plains 
of dry land. Most of their names are fanci- 
ful, such as Oceanus Procellarum (Ocean of 
Storms), Mare Tranquillitatis (Sea of Tran- 
quillity), and Mare Imbrium (Rainy Sea). 



WHAT THE MOON IS LIKE. U5 

These level regions cover about one-thirc 1 
of the part of the moon which we can see, 
for, as will be shown presently, we never 
see but one side of the moon. No seas, lakes, 
nor rivers are visible anywhere; indeed, so 
far as we know, there is no water at all in 
the moon and no atmosphere or layer of air 
around it. There can then be no clouds, dew, 
nor rain, and therefore no life, vegetable or 
animal, such as we know on the earth. 

The surface, as seen through a strong tele- 
scope, looks like a desert waste, as rough and 
arid as a volcanic region on the earth, cov- 
ered in parts with rugged mountains and 
craters. The moon mountains are different 
however, from those on the earth, being gen- 
erally in the form of rings encasing a plain, 
from which rise cone-like peaks of a lower 
height ; and sometimes there is only a single 
round peak in such a plain. Many of the 
mountains look like the craters of dead volca- 
noes, but no living volcanoes have been found, 
although some astronomers have thought 
that they saw signs of life in some of them. 

The picture (40) gives a general view of a part 
of the surface of the moon, as seen through a 
strong telescope, showing the ring mountains 
and, in some cases, the peaks within them. 




4 o The Moon's Surface, as seen through a Telescope. 
[Newcomb and Holden's Astronomy.] 



116 



WHAT THE MOON IS LIKE. \\*J 

The height of many of the moon mountains 
has been measured as carefully as that of moun- 
tains on the earth, and some of them have 
been found to be nearly as high as the highest 
ones on the earth (25,000 to 30,000 feet, or 
more than five miles). They are, therefore, 
really higher in proportion, because the moon 
is so much smaller than the earth. All these 




41. Showing that the Moon always has the same side toward 
the Earth. E, Earth; A, side of Moon always toward 
the Earth; B, side always from the Earth. 

mountains, like the great plains, have been 
laid down in the maps and named, mostly 
after great philosophers and astronomers, 
such as Newton, Herschel, and Kepler. 



Il8 YOUNG FOLKS' ASTRONOMY. 

In looking at the moon we always see the 
same spots in nearly the same places on its 
surface, and from this we know that it always 
presents the same face to us, and one side of 
it is never seen by us. If you walk round a 
table, always keeping your face toward the 
middle of the table, you yourself will turn 
completely round once in going round the 
table once ; yet only one side of you will ever 
be toward the table. Now call yourself the 
moon and the table the earth, and you will 
easily understand how the moon can turn on 
its axis once while going round the earth once, 
and why it is that we never see but one side 
of it. For certain reasons, which will not now 
be explained, we really see a little more than 
half of the moon's surface, so that only about 
three sevenths of it is hidden from us. 

The moon has therefore two motions : first, 
a motion round the earth, in which it presents 
to us its different phases, passing from new 
moon to full moon and back to new moon 
again in about twenty-nine and a half days ; 
second, a motion round its axis, turning round 
once in just the same time. As the spinning 
round of the earth on its axis makes day and 
night on the earth, so the turning of the moon 
makes day and night in the moon ; but while 



WHAT THE MOON IS LIKE. II9 

our day is only twenty-four hours long, the 
moon day lasts a month, each day and each 
night being nearly fifteen of our days in length. 
During the long day, with the sun always 
shining, the heat must be very great; and 
during the long night, when no sun warms it, 
the cold must be terrible. There is no twi- 
light there before sunrise and after sunset, as 
on the earth, but day begins and night comes 
on almost at once. 

RECITATION FOR LESSON XVII. 
How does the moon look through a telescope? 

Its surface is seen to be covered with moun- 
tains, valleys, and plains. 
What were its plains once thought to be? 

They were thought to be seas, and they are 
still called seas on maps of the moon, though 
they are now known to be only dry land. 
Is there no water on the moon? 

None can be seen by us, and no atmosphere 
or layer of air has been found around it. 

What follows from this? 

That there can be no clouds, dew, nor rain, 
and therefore no life such as we have on the 
earth. 

What is the general appearance of the moon? 

It looks like a desert waste, covered in parts 
with rugged mountains. 



120 YOUNG FOLKS' ASTRONOMY. 

Are there any volcanoes to be seen? 

Many of the mountains are hollow at the 
top like volcanoes, but no living volcanoes 
have been seen in the moon. 

Have the heights of any of these mountains been meas- 
ured? 

Yes; and they are higher in proportion 
than mountains on the earth. 

What other motion has the moon besides its motion 
around the earth? 

It turns round once on its axis while going 
round the earth. 

What happens from this? 

That the same side is always toward us, 
and we therefore never see the other side of 
the moon. 

Do we not really see a little more than half of it? 

Yes, we see about four sevenths ; so only 
three sevenths are hidden from us. 

Is there any day and night on the moon? 

Yes ; but the day there is about a month 
long, each day and each night being nearly 
fifteen of our days in length. 

Must it not also be hotter and colder there than on the 
earth? 

Yes ; during the long day the heat must be 
very great, and during the long night, when 
no sun warms it, the cold must be terrible. 



LESSON XVIII. 

ECLIPSES OF THE MOON. 

The earth, while revolving in its orbit 
around the sun, always casts a great shadow 
in the heavens on the opposite side from the 
sun ; and when the moon, moving in its orbit 
around the earth, comes into this shadow we 
say that the moon is in eclipse. 

We shall understand this better if we return 
once more to our lamp and orange, the for- 
mer of which, placed in the middle of the 
table, stands for the sun and the latter, near 
the edge of the table, for the earth. The 
lamp lights up only one side of the orange, 
leaving the other side in shadow. If you hold 
a sheet of paper behind the orange you will 
see that the shadow cast upon it is as round 
as the orange itself. Move the sheet of paper 
back from the orange little by little, and the 
shadow on the paper will become smaller and 
smaller until it finally ends. You will thus 
see that the shadow behind the orange is 
shaped like a cone — that is, large and round 
at one end and coming toward a point at the 



122 



YOUNG FOLKS' ASTRONOMY. 



other, something like a sugar-loaf. Now hold 
a small plum hung on a string to represent 
the moon in the shadow, and it will be wholly 
cut off by the shadow of the orange from the 
light — that is, it will be in eclipse. 

It is the same with the shadow of the earth. 
Since the sun is much larger than the earth, 
and the earth is round, the shadow of the 
earth must be like a cone, whose point is on 
the side opposite to that on which the sun 



,\ -.;•/' 




42. Total Eclipse of the Moon. 

shines. The length of this shadow is more 
than three times the distance of the moon 
from the earth, and when the moon in pass- 
ing in its orbit round the earth comes into it 
the rays of the sun are cut off from it, and as 
the moon has no light of its own, it is hidden 
in this shadow, or eclipsed. This can easily be 
seen in the picture (42), where S is the sun, E 
the earth, and M the moon ; the moon, cut off 



ECLIPSES OF THE MOO//. 1 23 

from the sunlight by the shadow of the earth, 
is in eclipse. It will be remembered that 
when the moon is on the opposite side of the 
earth from the sun, so that the earth is be- 
tween the two, the moon is said to be in oppo- 
sition, and it is then full moon. This is the 
only time that an eclipse of the moon can take 
place, because the moon must have its bright 
side toward us to be eclipsed. Of course, 



43. Partial Eclipse of the Moon. 

when its dark side is toward us there is no 
moonlight to be eclipsed. 

As the moon is in opposition once every 
month, it may seem to you that there ought 
to be an eclipse every month. This would be 
so if the moon passed exactly behind the earth, 
each time it goes round; but it sometimes 
passes a little above and sometimes a little 
below the cone of the earth's shadow, and 
then of course there is no eclipse. Sometimes 



124 YOUNG FOLKS' ASTRONOMY. 

it passes through the edge of the shadow, so 
that only part is cut off from the sunlight, and 
the eclipse is then said to be partial (43) ; but 
when the whole of the moon enters into the 
earth's shadow, the eclipse is said to be total. 
The length of a total eclipse differs according 
to the part of the shadow through which the 
moon passes. If it goes through the middle 
of the shadow, which is about three times as 
broad as the moon itself, it may be in eclispe 
nearly two hours ; but the time is generally 
much less. 

Although the eclipse is called total when 
the whole of the moon is in the earth's 
shadow, the moon is not always entirely hid- 
den from view when eclipsed ; for, though 
this sometimes happens, it is very rare. It 
usually appears, when in the middle of the 
shadow, of a dull copper-red hue, something 
like the color of the sun when looked at 
through smoked glass. When the eclipse is 
partial, only the part within the shadow is of 
this dark color. 

Let us once more return to our lamp and 
orange. By holding the sheet of paper again 
so that the shadow of the orange will fall on 
it, we shall see that there is a kind of half- 
shadow all around the real shadow of the 



ECLIPSES OF THE MOON. 1 25 

orange. There is a like half-shadow all 
round the cone-shaped shadow of the earth. 
This, which is called the penumbra (Latin pene y 
almost, and umbra, a shadow), 'is where only 
a part of the sun's rays are cut off by the earth. 
When the moon is in the penumbra it is only 
partly hidden, and is not of so dark a color as 
when in the shadow itself. Sometimes the 
moon passes partly within the penumbra 
without touching- the true shadow at all ; in 
such an eclipse it is not much darkened. 

It is during a partial eclipse of the moon, 
that the shadow of the earth can be seen, 
and it is from this that we get one of the 
proofs that the earth is round like a globe or 
sphere (see Lesson 2). When the moon en- 
ters only partly into the shadow of the earth, 
the rounded edge of the shadow can be seen 
on the bright part of the moon ; this edge, if 
continued round, would form a circle, and we 
thus get the shape of the shadow, just as we 
did when we held the sheet of paper behind 
the orange. As only a round thing casts a 
round shadow, we conclude that the earth 
must be round. 



126 YOUNG FOLKS" ASTRONOMY. 



RECITATION FOR LESSON XVIII. 
When is the moon said to be in eclipse? 

When it is in the shadow of the earth. 

What do you mean by the shadow of the earth ? 

The earth always casts a great shadow in 
the heavens on the opposite side from the 
sun. 
What is the shape of this shadow? 

Cone-shaped — that is, round and pointed at 
one end like a sugar-loaf. 

Is it not very long? 

Yes, it is more than three times as long as 
the distance from the earth to the moon. 

When only can the moon be eclipsed? 

When it is in opposition, when the earth is 
between it and the sun; because the moon 
must have its bright side toward us to be 
eclipsed. 

As the moon is in opposition once every month, why is 
it not eclipsed every month? 

Because the moon does not always pass ex- 
actly behind the earth each time it goes round ; 
it sometimes passes a little above and some- 
times a little below the earth's shadow, and 
then of course there can be no eclipse. 

What is a partial eclipse of the moon? 

When the moon passes through the edge of 



ECLIPSES OF THE MOON. 1 27 

the shadow, so that only part of it is cut off 

from the sunlight. 

What is a total eclipse of the moon? 

When the whole of the moon enters into 
the earth's shadow. 

Is the moon entirely hidden when in total eclipse? 

Sometimes, but very rarely. 
What does it usually look like when wholly in the 
earth's shadow? 

It has a dull copper-red hue, like the color 
of the sun when seen through smoked glass. 

What is the penumbra of the earth's shadow ? 

A kind of half-shadow all round the cone- 
shaped shadow of the earth. 

How does the moon look when in the penumbra ? 

It is only partly hidden, and is not of so 
dark a color as when in the shadow Itself. 

When can we see the shadow of the edge of the earth 
on the moon? 

When the moon is in partial eclipse. 

What is the shape of this shadow ? 

Rounded so that if continued around it will 
form a circle. 
What do we conclude from this? 

That as the shadow of the earth is round, 
the earth itself must be round. 



LESSON XIX. 

ECLIPSES OF THE SUN. 

We have seen, in the last chapter, that an 
eclipse of the moon can take place only when 
the moon is in opposition — that is, on the 
opposite side of the earth from the sun, when 
the earth is between it and the sun ; we have 
now to learn that an eclipse of the sun can 
take place only when the moon is in con- 
junction — that is, at new moon, when the 
moon is between the sun and the earth. As 
an eclipse of the moon is caused by the 
shadow of the earth on the moon, so an 
eclipse of the sun is caused by the shadow of 
the moon falling on the earth. 

We can easily see this by going back to 
our lamp and orange again. Tie a small ball, 
about as large as a plum, to a thread, to rep- 
resent the moon, and hold it near the orange 
between the lamp and the orange (standing 
for the sun and the earth as before), as shown 
at C in the picture (44), so that its shadow will 
fall on the orange. If you could put your 
eye on the spot where the shadow falls, you 



ECLIPSES OF THE SUN. 1 29 

would not be able to see the lamp, which 
would thus be totally eclipsed. 

The moon, at certain times, casts just such 
a shadow on the earth as the plum casts on 
the orange ; and to all who are within that 
shadow the sun will be in total eclipse. An 
eclipse of the moon is seen in all parts of the 
earth where it is night at the time and the 




44. Eclipse of the Sun, shown with Lamp and Orange. 

moon is above the horizon ; but it is different 
with an eclipse of the sun. The shadow of 
the moon, like that of the earth, is cone- 
shaped, but as the moon is much smaller 
than the earth, its shadow is only large 
enough to cover a small part of the earth's 
surface. There is also a penumbra or half- 
shadow around the dark shadow of the moon, 



130 YOUNG FOLKS' ASTRONOMY. 

just as there is about the shadow of the earth. 
In the picture both the shadow and the pen- 
umbra are shown. The eclipse will be total 
only where the dark shadow falls ; it will be 
partial at any place, such as B, within the 
penumbra, and there will be no eclipse at all 
in places outside of the penumbra. Total 
eclipses of the sun are therefore very rare at 
any one place on the earth's surface, but as 
astronomers are able to tell us where the 
shadow of the moon will fall, we can easily 
see one by going to the right place. There 
will be eight more total eclipses of the sun in 
this century, but none of them will be visible 
in the United States. The first one which 
will be seen in this country will take place 
May 28, 1900. 

As the moon is not always at the same dis- 
tance from the earth, it is sometimes so far 
away that its shadow cannot reach the earth's 
surface. There will then be no total eclipse 
of the sun at the place where the shadow 
would fall if it were long enough, for the 
moon will cover only the middle of the sun, 
leaving its edge visible all round it like a 
bright ring of light. Such an eclipse is called 
an annular eclipse — that is, a ring eclipse. 
The appearance of the sun during an annular 



ECLIPSES OF THE SUN. 131 

eclipse is shown in the picture (45), where the 
round shadow of the moon is seen nearly 
covering the disk of the sun. 

If the moon always passed exactly between 
the earth and the sun, there would be an 
eclipse of the sun every month at new moon ; 
but it sometimes passes above and sometimes 




45. Annular Eclipse of the Sun. 

below a line between them, and when it does, 
there can be no eclipse. An eclipse of the 
sun is seldom total at any one place more 
than four or five minutes, and never more 
than eight minutes; but the entire eclipse, 
from the time the moon begins to cover the 
sun to the time it leaves it, may be two or 
three hours. There are more eclipses of the 



132 YOUNG FOLKS' ASTRONOMY. 

sun than of the moon, but as sun eclipses are 
seen on only a small part of the earth, while 
moon eclipses are visible over a whole hemi- 
sphere at a time, more of the latter than of the 
former are seen at any one place. 

When there is a total eclipse of the sun 
night seems to fall in the day-time. Though 
the darkness is really less than when the full 
moon is shining, it appears to be much greater 
on account of the sudden change from day- 
light to darkness. A gloom spreads over 
everything, the darkness has a purple or 
violet tinge, and the air feels cool. Animals 
bleat and bellow, fowls and birds cease their 
songs and go to roost, and crickets begin to 
sing as if night had really come. When the 
sun is wholly hidden by the moon, the moon 
looks as if it were surrounded by a crown of 
silvery or pearly light. From this, which is 
called the corona (Latin for crown) and which ? 
we have learned, is made by the light of the 
sun, reddish flames are often seen to dart out 
to a great distance, looking like tongues of 
fire. 

In ancient times, before the cause of eclipses 
was known, people used to be greatly terrified 
when they took place. In some countries it 
was believed that a great dragon swallowed 



ECLIPSES OF THE SUN. 1 33 

the sun, and drums and gongs were beaten, 
and all kinds of noises were made to drive 
the beast away, and this is done even now in 
Persia and China. In others, it was thought 
that war, famine, and sickness were caused 
by eclipses ; and some people even saw in 
them the end of the world. But all such 
superstitions have now passed away, except- 
ing among the ignorant, for we not only 
know the exact cause of eclipses, but we can 
even tell when eclipses will take place many 
years ahead of their time. 

We can also tell the date of eclipses which 
took place thousands of years ago, and in this 
way some important dates in history have 
been found out. Thus Herodotus tells about 
an eclipse of the sun which took place when 
a battle was going on between the Lydians 
and the Medes. Herodotus does not give 
the date, and other writers give it different 
times between 583 B.C. and 626 B.C. But a 
British astronomer found out by calculating 
backward that the only eclipse of the sun 
between-those dates at that place must have 
taken place May 28, 585 B.C., and so we know 
that the battle must have been fought on that 
day. 



134 YOUNG FOLKS' ASTRONOMY. 

RECITATION FOR LESSON XIX. 
When is the sun said to be in eclipse ? 

When its light is hidden from us by the moon. 

When only can the sun be eclipsed ? 

When the moon is in conjunction — that is, 
between the sun and the earth. 

Does the moon then cast a shadow like that of the earth? 

Yes, it casts a cone-shaped shadow ; but as 
the moon is much smaller than the earth, its 
shadow is much smaller. 

Is it large enough to cover all the earth ? 

No ; it is only large enough to cover a 
small part of the earth's surface at once, and 
only those who happen to be where the 
shadow falls will see the sun in eclipse. 

Is it not different with an eclipse of the moon ? 

Yes, an eclipse of the moon is seen in all 
parts of the earth where it is night at the 
time and the moon is above the horizon. 

Has the moon's shadow also a penumbra ? 

Yes, it has a half-shadow around it, just as 
the shadow of the earth has. 

Where will an eclipse of the sun be total ? 

Only where the dark shadow of the moon 
falls. 

Where will an eclipse of the sun be partial ? 

At any place within the penumbra. 



ECLIPSES OF THE SUN. 1 35 

Are not total eclipses of the sun very rare at any one 
place on the earth's surface ? 

Yes ; but as astronomers are always able to 
tell where the shadow of the moon will fall, 
one can easily be seen by going to the right 
place. 

What happens when the moon is so far away that the 
shadow of the moon does not reach the earth ? 

The moon will then cover only the middle 
of the sun, leaving its edge visible all round it 
like a bright ring of light. 

What is such an eclipse called ? 

An annular eclipse— that is, a ring eclipse. 
Why is there not an eclipse of the sun every month ? 

Because the moon does not always pass 
directly between the sun and the earth, but 
sometimes above and sometimes below a line 
between them. 

How do the sun and moon look when the sun is in total 
eclipse ? 

The face of the sun is wholly hidden by the 
moon, which looks black ; and all around the 
edge of the moon is seen a crown of light, 
called the corona, from which reddish flames 
ire often seen to dart out like tongues of fire. 

Is it not quite dark during a total eclipse ? 

Yes, it is almost as dark as night, and the 
air is quite cool. 



LESSON XX. 

THE SOLAR SYSTEM. 

We have thus learned that the sun is the 
great centre around which the earth turns in 
its orbit. 

We have now to learn that the earth is only 
one of a family, of which the sun is the head, 
all the members of which move round the 
sun in like orbits, but at different distances 
from it. The earth and the other members 
of the sun's family are called planets or wan- 
derers, the word planet being made from a 
Greek word meaning to wander. They were 
thus called by the ancients because they ap- 
pear to wander in the heavens amongst the 
stars ; and we still give them the name, al- 
though we know that they do not really wan- 
der, but move in regular orbits round the 
sun. 

The family of the sun, consisting of the 
earth and the other planets, and a few other 
bodies, occupies a place alone by itself in the 
heavens, and is entirely separate from what 
we commonly call the stars. When we look 



THE SOLAR SYSTEM. 13/ 

up into the heavens at night we see what 
looks to be an immense dark vault spangled 
over with stars, among which move the moon 
and the planets which are in sight. Though 
some look larger and some smaller than 
others, they are all apparently at about the 
same distance from us, and planets and stars 
look nearly alike ; but they really differ from 
each other in many things, and the stars look 
like the planets only because the stars are at 
an immense distance. 

When looked at through a telescope the 
planets are seen to be globes or spheres, solid 
round bodies like the earth, while the stars 
still appear to be twinkling points of light, 
much as they do to the naked eye. The stars 
too never change their places in the heavens. 
You must not understand that they never 
move at all : what is meant is that they never 
change their places in regard to each other — 
that is, that they keep the same arrangement 
in the heavens all the time ; while the planets, 
which are always moving in their orbits, are 
sometimes near one group of stars and some- 
times near another. The stars too, as you 
will learn by and by, are hot bodies which 
shine by their own light, like the sun ; while 
the planets, like the moon, are cool bodies, 



138 YOUNG FOLKS' ASTRONOMY. 

having no light of their own, but only reflect- 
ing the light of the sun. 

Let us now leave the stars for a while and 
study the sun and the planets, which I have 
told you form a separate family by them- 
selves and occupy a separate place in the 
heavens — wholly distinct from the rest of the 
heavens, as much so as the United States is 
from the other countries of the earth. This 
group, which we will call a family, because the 
sun is the great head on which all the others 
depend, is commonly known as the solar 
system — that is, the system or group of the 
sun. 

Besides the earth, there are seven principal 
planets which move in orbits round the sun. 
They are named, after the gods of the ancients, 
Mercury, Venus, Mars, Jupiter, Saturn, Ura- 
nus, and Neptune. The first five have been 
known from the oldest times, and were so 
named by the ancients : but Uranus was not 
discovered until 1781 and Neptune until 1846. 
Mercury, Venus, and Mars are smaller than 
the earth, the others much larger. The first 
two, Mercury and Venus, are called interior 
(inside) planets because their orbits are inside 
that of the earth ; and Mars, Jupiter, Saturn, 
Uranus, and Neptune are called exterior (out- 



THE SOLAR SYSTEM. 1 39 

side; planets because their orbits are outside 




46. Comparative sizes of the Planets. 

that of the earth. Some idea of the different 
sizes of the planets, as compared with each 



HO YOUNG FOLKS' ASTRONOMY. 

other, may be formed from the picture (46), in 
which they are shown, as they would appear 
if they were all at the same distance from us. 

The eight planets, then, are all the time 
moving round the sun in great circular paths 
called orbits, all of which are at different 
distances from the sun. We have already 
learned that the earth's orbit is about ninety- 
two million (92,000,000) miles from the sun, 
and we have tried to form some idea of this 
immense distance; but the distance of the 
orbits of some of the exterior planets is as 
much greater than this, as this is greater than 
the distances on our earth. Although it is 
almost impossible for us to form any idea of 
these distances, they are all given in the table 
on page 170, as they may be convenient to re- 
fer to. 

Besides these great planets, most of which 
are plainly visible to the unaided eye, there 
are many smaller ones, which can be seen 
only through a telescope. Of these, which are 
called asteroids, more than two hundred have 
been discovered, and there are probably many 
more. They all move round the sun in orbits 
between those of Mars and Jupiter. 

We have already learned that our moon is 
a satellite or attendant of the earth, around 



THE SOLAR SYSTEM. 141 

which it is continually moving in an orbit 
while the earth is moving- round the sun. 
But the earth is not the only planet which is 
thus attended, and some of the planets are 
even better off than we are. Thus, Mars has 
two moons or satellites, Jupiter four, Saturn 
eight, and Uranus four ; but Neptune, the 
most distant of all the planets from the sun, 
has, like the earth, only one, and Mercury and 
Venus, the nearest ones to the sun, have 
none. 

RECITATION FOR LESSON XX. 

Is the earth the only body which revolves around the 
sun? 

No ; the earth is only one of several bodies 
called planets. 

Why are they called planets ? 

The word planet means wanderer, and these 
bodies were so named by the ancients because 
in moving in their orbits around the sun they 
appear to wander among the stars, which 
move so slowly that they appear never to 
move at all. 

Are the sun and the planets near the stars ? 

No; they occupy a place in the heavens 
alone by themselves, wholly separate from the 
places of the stars. 



142 YOUNG FOLKS' ASTRONOMY. 

Why then do they appear to be near each other ? 

Because they are at such vast distances 
from us. 

Do not the planets and the stars look much alike ? 

They do to the unaided eye ; but when 
looked at through a telescope the planets are 
seen to be globes or spheres like the earth, 
while the stars still appear to be twinkling 
points of light, much as they do to the eye 
alone. 
In what else do the planets differ from the stars ? 

The planets are cool bodies, like the moon, 
which have no light of their own, but only 
reflect the light of the sun ; while the stars 
are hot bodies, like the sun, which shine by 
their own light. 
What is the group of the sun and its planets called ? 

The Solar System — that is, the system or 
group of the sun. 

How many principal planets are there in the Solar 
System ? 

Eight ; namely, Mercury, Venus, the Earth, 
Mars, Jupiter, Saturn, Uranus, and Neptune. 

Are they all at the same distance from the sun ? 

No ; the orbits in which they revolve are 
all at different distances from the sun, that of 
Mercury being nearest and that of Neptune 
farthest from the sun. 



THE SOLAR SYSTEM. 1 43 

Are they ail of the same size ? 

No ; Mercury, Venus, and Mars are smaller 
than the earth, the others many times larger. 

Which ones are called the interior planets ? 

Mercury and Venus, because their orbits 
are inside that of the earth. 

Which are called the exterior planets ? 

Mars, Jupiter, Saturn, Uranus, and Nep- 
tune, because their orbits are outside that of 
the earth. 

Are there not also many smaller planets ? 

Yes ; the asteroids, whose orbits are be- 
tween those of Mars and Jupiter. 

How many moons have the principal planets ? 

Mars has two moons or satellites, Jupiter 
four, Saturn eight, Uranus four, and Neptune, 
like the earth, only one ; Mercury and Venus 
have none. 



144 YOUNG FOLKS' ASTRONOMY. 



LESSON XXI. 

MOTION OF THE PLANETS IN THEIR ORBITS. 

We have now learned that the sun and the 
planets (including the earth) which move 
around it form a family or group by them- 
selves, called the Solar System, which occu- 
pies a separate place in the heavens, entirely 
apart from any of the bodies called stars. As 
it is almost impossible to form from figures 
alone any idea of the sizes of the planets com- 
pared with each other, it is best to have some- 
thing on a smaller scale to compare them 
with. In the picture (46) in the last lesson their 
different sizes were shown as they would ap- 
pear if they were all placed at the same dis- 
tance from us ; but we do not get any idea 
from this of their different distances from the 
sun. We must therefore try another plan. 

Suppose then that we put in the middle of 
a large level field a ball about two feet wide 
and call it the sun. Now let us walk forty- 
one steps (82 feet : supposing that we go two 
feet at each step) from this ball and lay down 
a mustard seed, which will be the proper size 



MOTION OF THE PLANETS. 1 45 

for Mercury. Walk thirty steps farther (142 
feet from the sun), and lay down a pea of 
average size for Venus ; then thirty-six steps 
(215 feet from the sun) and lay down a little 
larger pea for the earth; and then fifty-six 
steps (327 feet from the sun) and lay down a 
very small pea for Mars. It will be. easy 
enough to place these at the proper distances 
from the sun, but the others are so much far- 
ther away that we may have some difficulty 
in giving them their proper positions. Jupi- 
ter will be rightly represented by a common- 
sized orange placed nearly a quarter of a mile 
away from the sun; Saturn by a somewhat 
smaller orange about two fifths of a mile 
away ; Uranus by a small plum more than 
three quarters of a mile away ; and Neptune 
by a little larger plum about a mile and a 
quarter away from the sun. Imagine all these 
to be turning round the sun in great circles, 
and we may possibly get some idea of the 
different sizes of the sun and the planets and 
their distances from each other. The aster- 
oids or minor planets, which move round the 
sun between Mars and Jupiter, cannot be 
shown, for they would be smaller than grains 
of sand. 

In the picture (47) is shown the sun and the 



I46 YOUNG FOLKS' ASTRONOMY. 

orbits of several of the planets. All cannot 
be shown, as it would take a very large sheet 
of paper to represent those farthest from the 
sun of the proper size. The moons or satel- 
lites of the planets are shown by dots near 
them. This picture shows the solar system 
not as we see it, but as it would appear to 
one looking at it from above. We on the 
earth see only a few of the planets at a time, 
and they appear as if they were moving along 
among thousands of stars ; but we must bear 
in mind all the while that this is only an ap- 
pearance, and that the stars, of which we 
shall learn more by and by, are much farther 
away from us than the planets. 

We have learned heretofore (Lesson 6) that 
what we call the weight of anything means 
simply the force with which the earth attracts 
or draws that thing to itself; and that it is 
this force which keeps everything on the 
earth — the water, the air, even us ourselves — 
as it rolls round in the heavens. We have 
also learned that it is not only the earth which 
attracts, but that everything on the earth 
has an attraction for every other thing, and 
that the larger a thing is the greater is its 
power to draw other things to it ; the earth, 
therefore, being so much larger than any- 



MOTION OF THE PLANETS. 1 47 

thing on it, attracts all other things with so 
much greater force that their attraction is 
not enough to be felt by us. We have now 




47. Plan of part of the Solar System. [Newcomb and 
Holden's Astronomy.] 

to learn that this ru^e holds good not only 
for all things on the earth, but also for every 
thing in the heavens : every thing or body is 



I4o YOUNG FOLK'S' ASTRONOMY. 

attracting or drawing toward itself all other 
things or bodies, and the larger the thing is 
the greater is the strength of its attraction. 

All the planets, then, attract each other; 
but the sun, which is about seven hundred 
times larger than all of them put together, 
attracts them much more strongly, so that 
everything in the Solar System is drawn 
with very great force toward the sun. But 
why, one may ask, if this is true, do not the 
earth and all the other planets get nearer and 
nearer to the sun all the time and at last fall 
upon it, just as a stone or other thing falls 
to the earth. 

This would be so if they were not all kept 
in their places by another force, which we 
must now learn about. Almost every child 
has seen stones thrown w^ith a sling. When 
we swing a sling with a stone in it about our 
head the stone goes round in a circle, of 
which the shoulder of the arm holding the 
string is the centre. The stone seems to pull 
on the string, and the harder we swing it 
the harder it pulls ; and if we let go of the 
string it flies away quickly. The force with 
which the stone pulls and tries to get away 
when we swing it round our head is called cen- 
trifugal (centre-flying, from Latin centrum. 



MOTION OF THE PLANETS. 



149 



centre, and fugere, to fly) force — that is, the 
force with which anything tries to ,fly off 
from the centre ; and it is nothing but the 
string which keeps it from thus flying off. 
The earth and the other planets turn round 




48. Centrifugal Force. ABC, circle in -which the stone 
moves when held by the string; A D, line in which it would 
move if the string be let go at A. 

the sun just as the stone goes round our hand 
when we swing the sling, and like the stone 
they are all the time trying to get away ; but 
they are all held in their orbits by the attrac- 
tion of the sun, which keeps them from flying 



I50 YOUNG FOLKS' ASTRONOMY. 

off just as the string of the sling keeps the 
stone, from flying off. These two forces then, 
gravitation and centrifugal force, by acting 
together keep the planets in their orbits: if 
there were no gravitation they would fly 
away into space, and if there were no centri- 
fugal force, they would fall into the sun. 

By the action of the same two forces the 
moon is made to turn round the earth; the 
centrifugal force keeps it from falling to the 
earth, and the force of gravitation or attrac- 
tion of the earth prevents it from flying away 
through the heavens. In the same way each 
satellite moves round its larger planet, kept 
in its path by these wonderful forces. 

RECITATION FOR LESSON XXI. 

If you should represent the sun by a ball two feet "wide, 
what would be the proper sizes of the four smaller 
planets ? 

Mercury would be of the size of a mustard 
seed, Venus of an ordinary pea, the earth of 
a little larger pea, and Mars of a very small 
pea. 

V7hat would be the proper sizes of the four larger 
planets ? 

Jupiter would be of the size of a common 
orange, Saturn of a smaller orange, Uranus of 
a small plum, and Neptune of a larger plum. 



■MOTION OF THE PLANETS. 151 

Of what size would the asteroids be ? 

Smaller than grains of sand. 

What have we learned to be the true meaning of weight ? 

Weight is the force with which the earth 
attracts or draws anything to itself. 

Do the things on the earth have an attraction for each 
other ? 

Yes, everything on the earth has an attrac- 
tion for every other thing, but the force of the 
attraction of the earth is so much greater that 
the attraction of the things on it is not felt by us. 

What rule can you make from this ? 

That the larger the thing is the greater is 
the force of its attraction. 

Is this true of things off of the earth as well as of things 

on it ? 

Yes ; the planets all attract each other, but 
the sun, which is about five hundred times 
larger than all the planets put together, at- 
tracts them much more strongly. 

Why then are not all the planets drawn to the sun, just 
as everything on the earth is drawn to the earth ? 

Because they are kept in their places by 
another force, called centrifugal force. 

What do you mean by centrifugal force ? 

The force with which any thing tries to fly 
off from the centre around which it turns; 
for instance, when I whirl a stone round my 



152 YOUNG FOLKS' ASTRONOMY. 

hand in a sling, the force with which the 
stone pulls on the string in trying to get 
away from my hand is centrifugal force. 

What keeps the stone from flying away ? 

The string which I hold in my hand. 

How can you explain the motion of the planets from 
this? 

The planets move round the sun just as the 
stone whirls in a circle round my hand ; and 
like the stone they are all the time trying 
to fly away, but they are held in their orbits 
by the attraction of the sun, just as the stone 
is held by the string. 

Are these two forces — the attraction of gravitation and 
centrifugal force — then equal to each other ? 

Yes; if there were no gravitation, the 
planets would fly away into space, and if 
there were no centrifugal force, they would 
all fall into the sun ; but the action of the two 
forces together keep them forever revolving 
in their orbits. 

Do these forces also explain the movements of the moon 
and of the satellites of the other planets ? 

Yes ; the attraction of the earth keeps its 
satellite from flying away, and centrifugal 
force keeps it from falling. It is the same 
with each of the other planets and its satel- 
lite or satellites. 



LESSON XXII. 

THE LESSER PLANETS. 

When looked at with the eye alone all the 
planets appear much alike ; but when viewed 
through a telescope the interior or inner 
planets, Mercury and Venus, show at different 



• < C C 



49. Appearance of Mercury at different Points of its Orbit. 
[Newcomb and Holden's Astronomy.] 

times phases like those of our moon — that is, 
they sometimes look like a crescent, some- 
times like a half globe of light, and sometimes 
like a full globe of light. These phases are 
caused in the same way as those of the moon, 
which are explained in Lesson XV. The 
planets, all of which, like the moon, shine by 



154 



YOUNG FOLKS' ASTRONOMY. 



reflecting the light of the sun, are light only 
on the side toward the sun. When either of 
them is between the earth and the sun, the 
dark side is toward us and we do not see it ; 
but as it moves along we soon see a crescent, 
which grows larger and larger until, when it 
is on the opposite side of the sun from us, the 




50. Transit of Mercury. 

whole of its bright side is toward us. But it , 
is then so far away from us, that it does not 
look so bright as when it shows less of its 
lighted side. 

It has been said that Mercury and Venus 
are not seen when their dark sides are toward 
us ; but there is one exception to this. Some- 
times in moving round the sun one of them 



THE LESSER PLANETS. 155 

passes directly between us and the sun, and we 
can then see it moving across the sun's face 
like a little black spot. Such a passage across 
the sun's face is called a transit of Mercury or 
Venus, whichever it may be. Astronomers 
take great pains to watch these transits, and 
costly expeditions are often sent to different 
parts of the earth to observe them, because 
they give us the best means of calculating the 
distance of the sun from the earth. 

Mercury. This planet is the nearest of all 
the planets to the sun, and is so hidden by the 
sun's light that it can seldom be seen except- 
ing just before sunrise and just after sunset. 
It shines with a bright white light, brighter 
than that of the stars. Its diameter or breadth 
is a little more than one third (about 3000 
miles) that of the earth, so that it would take 
about eighteen globes of its size to make one 
like the earth. It goes round the sun in its 
orbit once in eighty-eight of our days, so that 
the year in Mercury is only about three of 
our months long. It is supposed by some 
astronomers that it turns round on its axis 
once every twenty-four hours and five min- 
utes, which would make its day about as long 
as our day ; but this is not certainly known. 
Nor do we know whether its surface is made 



156 YOUNG FOLKS' ASTRONOMY. 

up of land and water like that of the earth, or 
is waterless like that of the moon, nor whether 
it has an atmosphere or not ; but, as it is so 
much nearer the sun than the earth is, it must 
get far more light and heat than we do. 

Venus. This, the second planet in distance 
from the sun, is nearly the same size as the 
earth, its diameter being seven thousand seven 
hundred (7700) miles. It goes round the 
sun once every two hundred and twenty-five 
(225) of our days, so that its year is about 
seven and a half of our months long. Some 
have thought that it turns on its axis once in 
twenty-three and a half hours, which would 
make its day only a little shorter than ours, 
but this calculation is not trusted by the best, 
modern astronomers. The axis of Venus is 
more slanted toward its orbit than that of the 
earth, and the changes of its seasons must 
therefore be greater than ours ; it gets, too, 
about twice as much heat as the earth does. 
Very little is known of the surface of Venus, 
but some think that there is water upon it, 
because there are many things which seem to 
prove that it has an atmosphere even denser 
than that of the earth. 

Venus is the brightest of the planets, and 
when most brilliant can be seen at midday by 



THE LESSER PLANETS. I 57 

the unaided eye. It can generally be seen 
just before sunrise or just after sunset, accord- 
ing to its position in its orbit. When it rises 
before the sun it is called the morning star, 
and when it sets after the sun the evening 
star. These names are very old ; the ancients 
believed that the morning and evening stars 
were two different stars, so they called the 
one Lucifer (light-bringer), and the other 
Vesper (evening star). 

The last transit of Venus — that is, its pass- 
age across the sun's disk — took place in 1 874 ; 
there will be another one in 1882, and after 
that none will take place for more than a hun- 
dred years. 

Mars. The earth comes next among the 
planets in point of distance from the sun, but 
as it has been described before we will pass 
on to Mars, the first of the exterior planets. 
Mars is six times smaller than the earth, its 
diameter being four thousand two hundred 
(4200) miles, or a little less than half that of 
the earth. Its year is nearly twice as long as 
ours, for it is twenty-three months in going 
round its orbit, and it has a change of sea- 
sons much like ours. It turns on its axis 
once every twenty-four and a half hours, 
thus making its day about the same as ours. 



158 YOUNG FOLKS' ASTRONOMY. 

As its orbit is outside that of the earth it can 
never pass between the earth and the sun, and 



51. Mars seen through a Telescope. [Newcomb and Hol- 
den's Astronomy.] 

it therefore does not pass through the differ- 
ent phases which Mercury and Venus do. 
Mars has a reddish tint when looked at with 



THE LESSER PLANETS. 1 59 

the eye alone ; but when examined through 
a telescope its surface around the equator is 
seen to be divided in color, some parts being- 
reddish and some greenish ; the former are 
supposed by some to be land and the latter 
water. Around the polar regions are also 
seen white spots, thought to be snow ; but all , 
these appearances are so doubtful that the 
best astronomers speak of them only as light 
and dark portions. It is believed, too, that it 
has an atmosphere ; but as it is further from 
the sun than the earth, it does not get so much 
heat and light as we do. But Mars is better 
off than the earth in one respect : it has two 
moons, while the earth has but one. These 
were not known before 1877, when they were 
discovered by Professor Asaph Hall, of Wash- 
ington. 

Asteroids. Next beyond Mars, between 
its orbit and that of Jupiter, are the orbits of 
the asteroids or minor planets, of which more 
than two hundred have been discovered, sev- 
eral being found almost every year. All of 
these are small, the largest being only from 
two hundred to four hundred miles in diame- 
ter, and the smallest from twenty to thirty 
miles. It would take several thousand of the 
size of the largest ones to make a planet as 



l6o YOUNG FOLKS' ASTRONOMY. 

large as the earth. Among" the principal ones 
are Ceres (discovered in 1801), Pallas (1802), 
Juno (1804), and Vesta (1807). Vesta is the 
only one ever seen with the unaided eye. 
Some astronomers have thought that the 
asteroids are the remains of a large planet 
broken into pieces by volcanic action or some 
other force, but this is not now believed to be 
probable. 

RECITATION FOR LESSON XXII. 
In what are Mercury and Venus like the moon ? 

They show phases like those of the moon. 

What is the cause of this ? 

As they shine, like the moon, only by 
reflecting the light of the sun, they are bright 
only on the side toward the sun. When either 
of them is between the earth and the sun, its 
dark side is toward us and we do not see it ; 
but as it moves along we see first a little of 
it, like a crescent, and finally, when it is the 
other side of the sun, the whole of it. 

Do we never see Mercury and Venus when their 
dark side is toward us ? 

Yes ; when either of them passes directly 
between us and the sun, we can see it moving 
across the sun's face like a black spot. 

What is such a passage called? 

A transit of Mercury or of Venus. 



THE LESSER PLANETS. l6l 

Why do astronomers take great pains to observe such 
transits ? 

Because they give the best means of calcu- 
lating the distance of the sun from the earth. 

Why do we seldom see Mercury? 

Because it is so near the sun that it is com- 
monly hidden by its light. 
How large is it, compared with the earth? 

It would take eighteen globes of the size of 
Mercury to make one as large as the earth. 

How large is Venus ? 

Nearly the same size as the earth. 

How bright is Venus, compared with other planets ? 

It is the brightest of the planets, and can 
sometimes be seen at midday with the unaided 
eye. 

When is it called the morning star? 
When it rises before the sun. 

When is it called the evening star? 

When it sets after the sun. 
What is the size of Mars, compared with that of the 
earth? 

It is six times smaller than the earth. 
How does Mars look when seen through a telescope? 

Its surface is covered with reddish and 
greenish spots, the former supposed to be 
land and the latter water ; and something 
white like snow is seen at the two poles. 



1 62 YOUNG FOLKS ASTRONOMY. 

Does it get as much heat and light as the earth ? 

No ; because it is farther from the sun. 

How many asteroids have been discovered ? 

More than two hundred, and new ones are 
found almost every year. 

Are they not all very small? 

Yes ; only one of them is large enough to 
be seen with the unaided eye. 



LESSON XXIII. 

THE GREATER PLANETS. 

Jupiter. Next to the orbits of the aster- 
oids is the orbit of Jupiter, the largest of all 
the planets — larger even than all the rest put 
together. It would take one thousand three 
hundred (1300) globes of the size of our earth 
to make one equal to that of Jupiter. Its 
diameter is about eighty-five thousand (85,000) 
miles. As it is about five times as far from 
the sun as the earth is, it has five times as far 
to travel in its orbit. It goes around this 
once every twelve of our years, and its year 
therefore is twelve times longer than ours. 
But it turns on its axis much faster than the 
earth, going round once every ten hours 
(9I1. 55m.)- Its days, then, are very short; 
and as its axis is only slanted a very little 
to the plane of its orbit, its days and nights 
are nearly equal in length, and there is there- 
fore very little change in its seasons. 

Next to Venus, Jupiter is the brightest 
of the planets. When looked at through a 
telescope, it has a light-yellowish color, with 



164 YOUNG FOLKS' ASTROXOMY. 

several grayish stripes or belts across it. 
These belts are all the time changing, from 
which it is supposed that we do not see the 
planet itself, but only a very cloudy atmos- 




Jupiter, seen through a Telescope, with a Satellite and 
its Shadow on it. 



phere around it ; that the bright parts are 
clouds lighted up by the sun, and that the 
dark belts are openings through these clouds 



THE GREATER PLANETS. 1 65 

showing either parts of the planet beneath or 
lower masses of clouds. 

Jupiter has four moons or satellites, which 
turn round it as our moon turns round the 
earth, but much more swiftly. The smallest 
one is about as large as our moon, and the 
largest one somewhat smaller than the planet 
Mars. These little moons cannot be seen 
with the unaided eye, but through a telescope 
they look like brilliant points of light. They 
were first seen by Galileo, the inventor of the 
telescope, in 1610. The astronomers of that 
time laughed at Galileo, and one of them said 
that to see moons around Jupiter one must 
have a telescope which would make them. 
Another one would not look through a tele- 
scope for fear that he should see them and 
have to change his mind. He died soon after 
without having seen them, which caused 
Galileo to remark : " I hope that he saw them 
while on his way to heaven." 

The orbits of Jupiter's moons are at differ- 
ent distances from the planet, the nearest one 
going round in less than two days and the 
farthest one in about twenty days. They 
often pass through the shadow which the 
planet makes in the side farthest from the 
sun, and are then said to be eclipsed. Their 



1 66 YOUNG FOLKS' ASTRONOMY. 

passages across the face of the planet, when 
they look like black spots on its bright sur- 
face, are called transits. 

Saturn. The most remarkable of all the 
planets is Saturn, whose orbit is next beyond 
that of Jupiter. It is the largest of all except 
Jupiter, its diameter being seventy thousand 
five hundred (70,500) miles, and its size about 




53. Saturn and its Rings, seen through a Telescope. 
[Newcomb and Holden's Astronomy.] 

seven hundred times that of the earth. .The 
year in Saturn is very long, as the planet 
goes round the sun but once in twenty-nine 
and a half years. It turns on its axis once in 
ten and a quarter hours, so that its day is 
nearly the same as that of Jupiter; but as 
its axis is more slanting than that of Jupiter, 
its days and nights are unequal in length, 



THE GREATER PLANETS. 1 67 

and it therefore has a regular change of sea- 
sons, each lasting more than seven of our years. 
Through a telescope Saturn looks much 
like Jupiter, having a cloudy atmosphere 
^arranged in belts ; but the most wonderful 
thing about it is its ring, which surrounds it 
opposite its equator. This ring is made up 
of two bright rings, one outside another, as 
shown in the picture (53), with a narrow dark 
line between them. Some think that there is 
a third darker ring inside, but this is not gen- 
erally believed to be a separate ring, but only 
the shading of the inner one. Though many 
thousand miles broad, Saturn's ring is only 
about one hundred and thirty-eight (138) 
miles thick, so that when the edge is toward 
us, as it is when the planet is in some posi- 
tions, it looks like a line of light. In the next 
picture (54) Saturn is shown moving in its 
orbit round the sun. It will be seen from 
this that its ring always slants the same way, 
which makes it easy to understand why it 
sometimes looks to us on the earth like a line 
of light, as it did in 1862 and in 1878. It is 
supposed that the ring is made up of a great 
number of little moons or satellites, all sepa- 
rate from each other, and all turning round in 
the same orbit. 



1 68 



YOUNG FOLKS' ASTRONOMY. 



Saturn has eight moons, of different sizes, 
which move round it in orbits outside of the 




ring. The largest of these is about the size 
of the planet Mercury. 



THE GREATER PLANETS. 1 69 

Of the planets known to the ancients, Saturn 
is the farthest from the sun ; but they knew 
nothing of its ring nor its moons, for these 
cannot be seen without a telescope, and to 
the eye alone it looks only like a bright star 
of a yellowish color. 

Uranus. The next planet to Saturn is 
Uranus, which was discovered to be a planet 
in 1 78 1 by Sir William Herschel. It is such 
an immense distance away that we know very 
little about it ; but it is about seventy-four 
times as large as the earth. It moves round 
the sun once in eighty-four (84) of our years, 
and it has four moons. It can be rarely seen 
with the eye alone ; through a telescope it 
looks bright, with a sea-green tinge, and is 
without any spots or belts. 

Neptune. This planet, the most distant 
of the sun's family, was discovered in 1846 
by Dr. Gaile, of Berlin. It is eighty times 
larger than the earth, and moves round the 
sun once in a hundred and sixty-five (165) 
of our years. Through a large telescope, 
Neptune, which cannot be seen by the eye 
alone, shows a round pale-blue disk. It has 
but one moon known to us, which revolves 
around it once in a little less than six days. 

The following table of the planets will be 
found useful to refer to : 



170 



YOUNG FOLKS' ASTRONOMY. 



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THE GREATER PLANETS. 17 1 



RECITATION FOR LESSON XXIII. 
Which is the largest of the planets? 

Jupiter ; it is larger than all the rest put 
together. 

How large is it, compared -with the earth? 

It is thirteen hundred times larger than the 
earth. 

How bright is it? 

Next to Venus it is the brightest of all the 
planets. 

How does Jupiter look through a telescope? 

Of a light-yellowish color, with grayish belts 
across it. 
What are these supposed to be? 

It is thought that we do not see the planet 
at all, but only its cloudy atmosphere ; that 
the bright parts are clouds lighted up by the 
sun, and the darker belts openings through the 
clouds. 

How large are the moons of Jupiter? 

The smallest one is about as large as our 
moon, and the largest one about the size 
of the planet Mars. 

When are they said to be eclipsed ? 

When they pass through the shadow which 



172 YOUNG FOLKS' ASTRONOMY. 

Jupiter makes on the side farthest from the 
sun. 

What planet is next beyond Jupiter? 

Saturn. 

How large is it ? 

, Next after Jupiter it is the largest of the 
planets. It is nearly seven hundred times 
larger than the earth. 

How does Saturn look through a telescope? 

Much like Jupiter, having also a cloudy 
atmosphere arranged in belts. 

What makes it the most wonderful of all the planets ? 
Its ring, which surrounds it opposite its 
equator. 

Of what is this ring made up ? 

Of two rings, one inside another, with 
spaces between them. 

Can Saturn's ring be seen with the eye alone ? 

No, it can be seen only through a telescope; 
and the inner part, which is much darker 
than the two outer parts, can be seen only 
with a very large telescope. 

How many moons has Saturn ? 

Eight, all of which revolve around it in or- 
bits outside of its ring. 

Are these moons very large? 

The largest one is about the size of the 
planet Mercury. 



THE GREATER PLANETS. 173 

Was Saturn known to the ancients ? 

Yes ; but they knew nothing of its ring nor 
of its moons. 
Did they not think it was the last of the planets ? 

Yes, for they did not know about Uranus 
and Neptune. 

How large is Uranus, compared with the earth? 

It is about seventy-four times larger than 
the earth. 

Is much known about it ? 

No, it is too far away to be seen very well ; 
but through a telescope it looks bright, with- 
out spots or belts. 

How many moons has it ? 

Four. 

What planet is farthest of all from the sun? 

Neptune. 

How large is it, compared with the earth? 

It is one hundred and five times larger than 
the earth. 

How many moons has it ? 

But one known to us. 



LESSON XXIV. 

COMETS AND SHOOTING STARS. 

Besides the planets and their satellites, 
which we have called the members of the 
sun's family, there are other bodies in the 
Solar System some of which are rather visi- 
tors than regular members of it. Among these 
are comets, those singular bodies sometimes 
seen with long fiery tails, and meteors, which 
are commonly called falling or shooting stars. 

Comets bright enough to be seen with the 
eye alone are generally made up of two parts 
— the head and the tail. The head consists of 
a bright centre, called the nucleus (Latin for a 
kernel), which looks much like a star, and 
which is surrounded by a fog or mist, bright 
near the nucleus, but shaded off at the edges. 
This foggy patch around the nucleus looks 
some like hair, and is therefore called the coma 
(Latin for hair), and from this comes our word 
comet. On the side farthest from the sun the 
coma extends in a long line of light, which 
usually grows wider and fainter as it gets far- 
ther from the nucleus, until it can no longer 



COMETS AND SHOOTING STARS. 175 

be seen. This, which is called the tail, is 
generally so thin that stars can be seen shin- 
ing through it. In some comets the tail is 
very long and bright, in some it is short and 
dim, and in others it is split into two or more 
tails. 

More than six hundred comets have been 
noted since the time of Christ, but there are 




55. Telescopic Comet without 56. Telescopic Comet with 
a Nucleus. a Nucleus. 

supposed to be many thousands of them, for 
several are seen with telescopes every year 
which are not bright enough to be seen with 
the unaided eye. Many of these telescopic 
comets are little more than patches of bright 
fog, having neither nucleus nor tail. The 
pictures show a telescopic comet without a 
nucleus (55), and one with a nucleus (56). 
Comets are not found in any particular part 
of the heavens, but are seen traveling every- 



i;6 



YOUNG FOLKS' ASTRONOMY. 



where. Some of them move always within 
the Solar System, and some appear to go far 
outside of it. They move round the sun in 
regular orbits— not circular, like those of the 
planets, but oval, so that they are sometimes 
very near the sun and sometimes at an im- 
mense distance from it. The picture shows 
the form of the orbit of a comet, S being the 
sun, and E the earth in its orbit. 




57. Orbit of a Comet. 

The orbits of some comets are so small that 
they go round the sun once every few years, 
while others are so large that they go round 
only once in several thousand years. Those 
whose orbits are so large must go far beyond 
the Solar System. Comets stay in sight 
sometimes for only a few days and sometimes 
for more than a year, but they are usually 
seen about two or three months. They are 
brightest when near the sun, and grow dim- 



COMETS AND SHOOTIXG STARS. 177 

mer and dimmer as they move away from it 
.until they go out of sight. 

We do not know exactly of what comets 
are made. Some have thought that they 
are merely masses of glowing gas, but it is 
now generally believed that the nucleus of a 
comet is either a solid body or a dense mass 
of small particles of matter, and that the coma 
or fog around it is made by the heat of the 
sun, which is so strong as to turn parts of the 
nucleus into vapor. The tail is supposed to 
be a stream of this vapor, rising from it like 
the smoke from a chimney. 

In ancient times, when men were more 
ignorant and superstitious than now, comets 
were objects of awe. They were believed to 
be the souls of great men, who, after living 
below a while after death, were at last carried 
to heaven in a kind of triumph. Thus the 
great comet which was seen at Rome a few 
years after the death of Julius Caesar was be- 
lieved to be the soul of that great man on its 
way to heaven. It was also thought that 
war, sickness, and famine were apt to follow 
the appearance of a comet, because it was a 
sign that the people were no longer to have 
the help of the soul thus carried away. Kings 
and princes looked upon comets as mes- 




58. 



Donati's Comet of 1858. [Newcomb and Holden's 
Astronomy.] 17 



COMETS AND SHOOTING STARS. 179 

sengers sent by the gods to warn them of 
trouble to come, or of some great event which 
was about to take place. When William 
Duke of Normandy was about to invade Eng- 
land (1066) a great comet shone in the sky, 
and this was taken as a good sign by him and 
his followers. In 168 1 Halley, an English as- 
tronomer, showed that this comet was the 
same one seen in that year. He showed also 
that it went round the sun once every seventy- 
six years, and foretold that it would be seen 
again in 1759. It was seen in that year and 
again in 1835, and is now known as Halley 's 
comet. It will be seen in the heavens again 
in 1911. 

Though in these days people generally are 
too sensible to believe that comets have any- 
thing to do with the affairs of men, some have 
thought that one of these wanderers may 
some time strike the earth and destroy it. 
But little is to be feared on this account : in 
1872 a comet came so near the earth as to 
touch its atmosphere with its tail, and all the 
harm it did was to give us a splendid shower 
of shooting tars. 

Shooting Stars. On clear nights, bright 
bodies like stars are sometimes seen to move 
quickly across the heavens and disappear 



l8o YOUNG FOLKS' ASTRONOMY. 

often leaving a streak of light for a few 
seconds behind them. These are commonly 
called shooting or falling stars, but they are 
not stars at all ; they are more properly called 
meteors, and those which fall to the earth, as 
some of them do, meteorites or aerolites. 

Meteors are now known to be small bodies 
moving through the heavens and around the 
sun in paths much like those of comets. 
Some are solid masses of stone or metal, some 
masses made up of small pieces, and others 
perhaps only bodies of gas. It is now be- 
lieved by the best astronomers that the 
heavens within the Solar System are full of 
these little flying bodies, which are so small 
that they cannot be seen when they are out 
of the earth's atmosphere. Anything which 
will burn may be set on fire by only blowing 
air very swiftly against it ; and a thing which 
will not burn may be thus made red-hot and 
perhaps melted. It is the same with things 
passing very swiftly through the air. So" 
when the earth comes near enough to any of 
these little meteors to bring them within its 
atmosphere, they are made red-hot in passing 
through the air at great speed and burn, and 
thus make the lights which we call shooting 
stars. The small ones are entirely burned 



COMETS AND SHOOTING STARS. l8l 

up, but sometimes one is large enough to pass 
through our atmosphere and fall on the earth. 
Some burst with a loud noise before reaching 
the earth, and fall in many small pieces ; and 
men and cattle have been killed by them. 

Shooting stars are usually seen in great 
numbers about the ioth of August and the 
13th of November, at which times they 
sometimes fall in showers. It has been found 
that they always come from certain parts of 
the heavens, and astronomers generally look 
for them about those times. They differ 
much in size and brightness, but are generally 
small, though some have been seen almost as 
large and as bright as the moon. 

It is believed by many that shooting stars 
or meteors differ from comets only in size ; 
indeed, some think that comets are only flocks 
of meteors traveling along in an orbit to- 
gether, and that shooting stars are some of 
the flock which are lost as the comet flies along. 

RECITATIONS FOR LESSON XXIV. '-■ 
What other members of the Solar System are there, 
besides the planets and their satellites? 

Comets and shooting stars. 

Of how many parts are comets which can be seen 
with the eye alone usually made up? 

Of two parts — the head and the tail. 



1 82 YOUNG FOLKS' ASTRONOMY. 

Of what is the head composed? 

Of a bright part called the nucleus, and of 
a misty part around it called the coma. 

From -what is the word comet made? 

From coma, which in Latin means hair, be- 
cause this part in comets looks some like hair. 

How is the tail formed? 

By the coma stretching out, on the side 
farthest from the sun, in a long line of light. 

Are the tails of all comets alike? 

No ; some are very long and bright, some 
short and dim, and others are split into two 
or more parts. 

Can all comets be seen with the eye alone? 

No ; by the telescope several are seen every 
year, some of which are only patches of light, 
with neither nucleus nor tail. 

Do comets move within the Solar System? 

Some always do, but some appear to go 
far outside of it. 
How do they move through the heavens? 

Around the sun in regular orbits ; not circu- 
lar, like those of the planets, but oval, so that 
they are sometimes very near the sun, and 
sometimes very far from it. 

Can we tell how long it takes a comet to go round in 
its orbit? 

Yes ; some go round once every few years, 



COMETS AND SHOOTING STARS. 1 83 

but the orbits of some are so large that they 
go round only once in several thousand 
years. 

Do we know of what comets are made ? 

Not exactly; but it is now generally be- 
lieved that the nucleus is either solid or a 
mass of small pieces, and that the coma is a 
part of the nucleus turned into vapor by the 
heat of the sun. 

What is the tail supposed to be? 

A stream of this vapor rising from the 
nucleus like smoke from a chimney. 

What are shooting or falling stars ? 

They are not stars at all, but small bodies 
moving around the sun in paths much like the 
orbits of comets. • 

What are they properly called? 

Meteors ; and those which fall to the earth 
meteorites or aerolites. 

Are not some of them solid ? 

Yes; some are solid masses of stone or 
metal, some masses made up of small pieces, 
and others perhaps only bodies of gas. 

Are meteors very numerous ? 

Yes ; the heavens within the Solar System 
are supposed to contain great numbers of 
them. They are generally so small that they 
cannot be seen, but when the earth comes near 



1 84 YOUNG FOLKS' ASTRONOMY. 

enough to any of them to bring them within 
its atmosphere, they become so heated that 
they burn and make shooting-stars. 

Do they burn up entirely? 

The small ones do, but sometimes a large 
one passes through our atmosphere and falls on 
the earth, or explodes and falls on it in pieces. 

When do shooting stars often fall in showers ? 

About the ioth of August and the 13th of 
November, when the earth passes through 
their orbit. 

Do not some think that meteors and comets differ only 
in size ? 

Yes ; and it is believed by some that comets 
are only flocks of meteors traveling along in 
an orbit together. 



LESSON XXV. 

THE FIXED STARS. 

Since the sun is the source of light and 
heat to the planets and the great centre 
around which they all revolve, it is the most 
important body in the Solar System ; but we 
must not conclude from this that it is the 
most important body in the universe. We 
have learned (Lesson XIX.) that the Solar 
System, vast as it is, occupies only a small 
part of the heavens, entirely isolated from the 
other parts ; and that the thousands of stars 
which bespangle the sky are beyond it, im- 
measurably outside of the orbit of the most dis- 
tant planet. We have also learned that these 
stars appear through a telescope much as 
they do to the unaided eye, though brighter : 
they always look like twinkling points of 
light, and never show a disk — that is, look 
round — as the planets do through a telescope ; 
indeed, none of them, even when viewed with 
the strongest telescopes, appear broad enough 
to be measured. Yet the light which they 
give is their own light, and not reflected light, 



1 86 YOUNG FOLKS' ASTRONOMY. 

like that of the planets and their moons ; and 
since their light is very bright and strong, and 
much like the light of our sun, we are led to 
believe that they are bodies of very great size, 
and that they appear small to us because they 
are at such immense distances away. 

There is good reason for believing that 
many of the stars are hundreds of times 
larger than our sun ; indeed, astronomers be- 
lieve that most of them are vast bodies giving 
out light and heat — that is, that they are suns 
like our sun — that nearly every one of them 
is the centre of a system like our Solar Sys- 
tem, and is surrounded by a family of planets 
which revolve around it, as the earth and 
other planets revolve round our sun. The 
strongest telescopes do not show any such 
planets around the stars, but even if there were 
any they could not be seen, because planets' 
light being only reflected light, is not strong 
enough to reach us from so great a distance. 

It may be thought that the stars are not far ' 
enough apart for each to be the centre of such 
a vast system as our Solar System, but they 
appear near together only because they are 
so far away. The distance of the nearest of 
them is more than five hundred thousand times 
the distance of our sun from the earth. Be- 



THE FIXED STARS. loj 

sides, it must be borne in mind that they are 
not all evenly placed over the surface of a 
great vault, as the ancients believed, but that 
some are behind others, so that, being in 
nearly the same line of sight, they appear to 
be near each other when they are really great 
distances apart. We may get some slight 
idea from this of the immensity of the uni- 
verse ; our earth, which seems so large to us, 
is little more than a grain of sand in the great 
Solar System, and the Solar System is not as 
much as a grain of sand in the vast universe, 
which is made up of countless numbers of 
such systems. 

The stars are commonly called the fixed 
stars, a name given to them by the ancients 
because they believed them to be fixed in the 
heavens. The fixed stars shine with very dif- 
ferent brightnesses ; while some are brilliant, 
others are paler, and some are so very dim 
that they can scarcely be seen. This has 
enabled astronomers to divide them into 
classes called magnitudes, the word referring 
not at all to their size, but only to their bright- 
ness. Stars which shine the brightest are 
called stars of the first magnitude, the next 
brightest stars of the second magnitude, and 
so on. There are only twenty stars of the 



155 YOUNG FOLKS' ASTRONOMY. 

first magnitude, but they increase in number 
very fast as their brightness grows less, as 
will be seen by the following table, which 
shows the number of stars in the first nine 
magnitudes : 

No. of No. of 

Mag. Stars. Mag. Stars. 



6th 3,200 

7th 13,000 

8th 40,000 

9th 142,000 



1st. 

2d 65 

3d 190 

4th 425 

5th 1,100 

Of these, only the stars of the first six 
magnitudes can be seen with the unaided eye, 
and only the best eyes can see the smaller stars 
of the sixth magnitude. We can see, with- 
out a telescope, on the clearest nights, only 
about three thousand stars, for we do not see 
all the heavens at once ; but when we look 
through a telescope, not only stars of the 
seventh, eighth, and ninth magnitudes are 
open to our view, but also millions of small 
stars of magnitudes below the ninth. The 
band of light stretching across the heavens, 
which is commonly called the Milky Way or 
Galaxy, is seen to be made up of an immense 
number of stars, apparently placed close to- 
gether, but which are probably at great dis- 
tances from each other. 

Besides the Milky Way, there are other 



THE FIXED STARS. I«9 

clusters of stars in different parts of the 
heavens, made up of stars crowded so closely 
together that they cannot be counted. Some 
of these clusters can be seen with the eye 
alone, and look much like pieces of the Milky 
Way ; but through a telescope they appear 




59. Star Cluster seen through a Telescope. [Newcomb and 
Holden's Astronomy.] 

like a host of stars, shining with a blaze of 
light. By the aid of the telescope can also 
be seen here and there dim patches of light, 
which cannot be seen with the eye alone, and 
some of which even the strongest telescopes 
cannot separate into stars. These are called 
nebulas, from the Latin word nebula, meaning 



IQO YOUNG FOLK'S' ASTRONOMY. 

a cloud. Most of the nebulae are nearly 
round, but some are long, almost like a 
straight line, and others are like rings or 
spirals. 

All the stars which can be seen with the 
unaided eye do not appear of exactly the 




60. Ring Nebula. [Newcomb and Holden's Astronomy.] 

same shade of color, some being ruddy, some 
yellowish, and some giving a white light ; but 
when viewed through the telescope many are 
seen to be. of bright colors, such as blood-red, 
orange-yellow, golden-yellow, and even blue, 
green, violet, lilac, gray, and olive. Some- 
times, too, stars are grouped together in twos, 



THE FIXED STARS. I9I 

threes, and fours, some of one color and some 
of another. By watching these double and 
triple stars for a long time, it has been found 
out that they turn round each other. If, then, 
these are the centres of systems like ours, and 
have planets revolving around them, the day- 
light on these planets, if seen with eyes like 
ours, is red, blue, and so on, according to 
the color of the sun which gives them light. 

RECITATION FOR LESSON XXV. 
Are any of the stars within the Solar System? 

No ; they are all far beyond the orbit of the 
most distant planet. 

How do the stars look through a telescope? 

Much as they do to the eye alone, but 
brighter ; they never look round like the plan- 
ets, but always like twinkling points of light. 
Do they shine by reflected light, like the moon? 

No ; they shine by their own light, like the 
sun. 
What do we conclude from this? 

That they are bodies of very great size, 
which appear small because they are so far 
away. 

Are not some of them thought to be larger than the 
sun? 

Yes, many hundred times larger; and as- 



192 YOUNG FOLKS' ASTRONOMY. 

tronomers believe that they are suns like our 
sun, which give out light and heat. 

Are they not also thought to have planets revolving 
round them? 

Yes ; and that each one of them is there, 
fore the centre of a system like our Solar 
System. 

If there are such planets, why can we not see them ? 

Because they are too far off, and shine only 
by reflected light, which is not strong enough 
to reach us. 

What are the stars commonly called? 

Fixed stars ; a name given them by the 
ancients, because they believed they were 
fixed in the heavens. 

How are the fixed stars divided by astronomers ? 

Into classes called magnitudes, according 
to their brightness. 

How many of these magnitudes can be seen with the 
unaided eye ? 

Only six ; and only the best eyes can see 
the smaller stars of the sixth magnitude. 

About how many stars can be seen at once on a clear 
night? 

Only about three thousand ; for we do not 
see all the heavens at once. 

But can we not see many more through a telescope? 

Yes; through a telescope we can see mil- 
lions which are not visible to the eye alone. 



THE FIXED STARS. 1 93 

Of what is the Milky Way or Galaxy made up ? 

Of an immense number of stars, which look 
as if they were close together, but which are 
probably great distances apart. 

Are there also separate clusters of stars in the heavens ? 

Yes ; some, seen with the eye alone, look 
like pieces of the Milky Way, but through a > 
telescope they appear like a host of stars shin- 
ing with a blaze of light. 

What are nebulae? 

Dim patches of light, which cannot be seen 
with the eye alone, and some of which even 
the strongest telescopes cannot separate into 
stars. 

Are the nebulas of different shapes? 

Yes; some are round, some straight, and 
some like rings or spirals. 
Are all stars of the same color ? 

No ; many are of bright colors, such as 
red, yellow, blue, and green. 

Are not different-colored stars sometimes grouped to- 
gether ? 

Yes ; sometimes in twos, threes, and fours, 
which revolve around each other. 

If these are suns and have planets revolving around 
them, what kind of light must these planets have ? 

Their day-light, if seen with eyes like ours, 
must be of the color of the sun which shines 
on them. 



LESSON XXVI. 

THE APPEARANCE OF THE HEAVENS. 

Though the fixed stars are at very different 
distances from us, let us imagine for the sake 
of convenience that they are fastened on 
the inside of a great globe, and all at the same 
distance from the earth, which is all the time 
turning round in the centre, this being the 
way in which they really appear to us. We 
on the earth can see of course only those stars 
which are opposite us, but as the earth turns 
round from west to east others are all the 
time coming into view in the east and appear- 
ing to move across the heavens toward the 
west, where they go down out of sight. Thus 
they appear to move from east to west 
because the earth moves the other way. 

Now suppose that the axis of the earth be 
lengthened from each of the poles in a straight 
line until the two ends touch the heavens: 
this will be the axis of the heavens, around 
which they appear to turn, and the ends will 
be the poles of the heavens. If we could stand 
directly on the north pole of the earth we 



APPEARANCE OF THE HEAVENS. 1 95 

should see half of the heavens, but it would 
always be the same half ; the same stars would 
appear to turn round and round the north 
pole of the heavens in circles, those near the 
pole moving in small circles and those nearer 
the horizon in larger ones, none ever going 
below the horizon. It would be the same at 
the south pole of the earth, only the other 
half of the heavens would be seen there ; but 
if we stood at the equator, we would see at 
once the half of the heavens from one pole to 
the other, and during the twenty-four hours 
of the day all the stars would pass through 
the heavens, appearing to rise in the east and 
set in the west. We would see them, of course, 
only at night, for in the day-time they are 
hidden by the brighter light of the sun, but 
they are there both day and night. 

To people living about the same distance 
from the north pole as New York, the heavens 
look a little different from their appearance at 
the poles or the equator. As we are nearly 
half-way between the north pole of the earth 
and the equator, the north pole of the heavens 
is about half-way between the horizon and the 
zenith, or point directly overhead. There- 
fore, while some of the stars appear to rise in 
the east and set in the west, those near the 



196 YOUNG FOLKS' ASTRONOMY, 

pole can be seen to move all the way round it 
in a circle, never going out of sight. This 




61. Showing the Apparent Daily Motion of the Stars round 
the Pole Star. [Newcomb and Holden's Astronomy.] 

can be better understood from the picture (61), 
which shows the north pole of the heavens 
and the stars around it. The star in the mid- 



APPEARANCE OF THE HEAVENS. 1 9/ 

die is the Pole Star, commonly called the 
North Star, because it is always in the north. 
All the stars within the circle move every day 
round the Pole Star and are always above 
our horizon ; and all without the circle move 
round in the same way, but they are so far 
from the pole that a part of their circles are 
below our horizon, and they therefore appear 
to rise and set. 

Thus different stars are seen by those on 
different parts of the earth ; and while some 
stars around the north pole of the heavens are 
always in our view, there are many stars at the 
south pole of the heavens which are never seen 
by us. We must also bear in mind that the stars 
which rise and set on our horizon are not 
always the same at all seasons of the year, 
but are continually changing. This is caused 
by the earth's motion round the sun; as it is 
night only on the side of the earth which is 
furthest from the sun, and as the earth is 
sometimes on one side of the sun and some- 
times on the other, it follows that one side of 
the heavens is opposite us in winter nights, 
and the other side in summer nights, and that 
the stars which we see in winter are different 
from those which we see in summer. It also 
follows that the stars around the pole which 



I9 S YOUNG FOLKS' ASTRONOMY. 

are always visible do not appear to us at the 
same time of night in the same positions, 
being sometimes on one side of the pole and 
sometimes on another. 

There are maps of the heavens called celes- 
tial (Latin ccelestis, from cceliun, heaven) maps to 
distinguish them from terrestrial (Latin terres- 
tris, from terra, the earth) maps, or maps of 
the earth, and also celestial globes on which 
all the principal stars are laid down, just as 
the principal places on the earth are marked 
on terrestrial maps and globes. As the 
stars all look much alike, differing chiefly in 
brightness alone, it has been found necessary 
to divide them into groups called constella- 
tions (Latin const ellatio, a group of stars). 
This was first done by the ancients, who gave 
the names of animals, of men, and of other 
objects to the constellations because they 
thought that they saw in the stars of which 
they were formed some likeness to those 
things. These names are still kept by us, ' 
although in most cases the groups of stars do 
not look anything like the things from which 
they are named. 

In beginning to learn astronomy one ought 
to learn the places in the heavens of the prin- 
cipal constellations so as to be able to know 



APPEARANCE OF THE HEA YENS. I99 

them at sight. It is best to have the use of a 
celestial globe or a set of celestial maps, but 
the beginner will be saved time and trouble if 
the teacher is able to point out the most 
important ones, and to show how they may 
be known. No telescope will be needed at 
first, as the principal constellations can easily 
be seen with the eye alone. 

Among the most important of the stars is 
the Pole Star, because it is always in the 
north, and from it therefore we can get the 
points of the compass. When we face it, the 
east is on our right hand, the west on our left, 
and the south behind us. When the sailor 
can see the Pole Star he can steer his ship in 
the course he wishes to go, even if he has no 
compass. It is therefore important to know 
how to find it, and to know this we must first 
learn to find the constellation called the Great 
Bear. 

RECITATION FOR LESSON XXVI. 
How do the stars really appear to us ? 

As if they were all fastened on the inside of 
a great globe, at equal distances from the 
earth in the centre. 

What makes them appear to be moving round the 
earth from east to west? 

The turning of the earth from west to east. 



200 YOUNG FOLKS' ASTRONOMY. 

What do you understand by the poles of the heavens ? 

If the axis of the earth were lengthened out 
at the poles until it touched the heavens at 
each end, the two ends where it touched 
would be the poles of the heavens, and the 
axis itself would be the line around which the 
heavens appear to turn. 

If we could stand at the north pole of the earth, 
how would the heavens appear ? 

We could see only the northern half of the 
heavens, and the stars would appear to move 
round and round the pole of the heavens in 
circles, none going below the horizon. 

Would it be the same if we stood at the south pole? 

Yes, only we should see the southern 
instead of the northern half of the heavens. 

How would the stars look if we stood on the equator ? 

Half of the heavens would be seen at once, 
stretching from pole to pole, and the stars 
would look as if they rose in the east and set 
in the west. 

Would not all of the stars thus pass through the i 
heavens ? 

Yes ; but we should see only those opposite 
us at night, those passing in the day-time be- 
ing hidden by the light of the sun. 

How do the stars look to people living about as far 
ftom the north pole as New York? 

As New York is nearly half-way between 



APPEARANCE OF THE HEAVENS. 201 

the north pole and the equator, the north 
pole of the heavens is about half-way between 
the horizon and the zenith. Therefore some 
stars appear to move round the pole and 
others appear to rise and set. 

What do you understand by the zenith ? 

The point in the heavens directly over our 
heads. 

Do we see the same stars at all seasons of the year? 

No ; they are always changing a little on ac- 
count of the earth's movement around the sun. 

Are the stars seen in winter the same, as those seen 
in summer? 

No ; they are entirely different : as it is 
night only on the side of the earth furthest 
from the sun, and as the earth in winter is on 
a different side of the sun from that on which 
it is in summer, it follows that different sides 
of the heavens are seen in winter and summer. 

Are not the stars around the pole always visible to us ? 

Yes ; but they do not always appear in the 
same positions, being sometimes on one side 
of the pole and sometimes on another. 

How are the stars divided on maps of the heavens? 

Into groups called constellations. 

Why did the ancients give these the names of men } 
animals, etc. ? 

Because they thought they saw in the stars 



202 YOUNG FOLKS' ASTRONOMY. 

of which they are made up some likeness to 
those things. 

Why is the Pole Star one of the most important ones 
to know ? 

Because it is always in the north, and from 
it we can get the points of the compass. 

What constellation must we know to find the Pole 
Star? 

The constellation of the Great Bear. 



LESSON XXVII. 

THE CONSTELLATIONS. 

The constellation of the Great Bear (Latin 
Ursa Major) is sometimes called the Plow, 
but more commonly the Dipper ; and though 
it does not look much like a bear or a plow, 
its stars may easily be imagined to form the 




62. The Great Bear. 

outline of a dipper with a bent handle, as will 
be seen in the picture. One who has once 
seen this will not be apt to forget it ; it is 
made up of seven bright stars, four of which 
form the bowl and three the handle of the 
dipper. The two stars on the side of the 
bowl furthest from the handle are called the 



204 YOUNG FOLK'S' ASTRONOMY, 

Pointers, for they point very nearly to the 
Pole Star. 

By looking at the picture on page 196 it 
will be seen that the constellation of the Great 
Bear or Ursa Major is within the circle en- 
closing the stars which are visible all the 
time at New York. It will also be seen bv 
the dotted line how the Pointers point to the 
Pole Star. The Pole Star apparently never 
changes its place, because it is at the end of 
the axis around which the heavens appear to 
revolve, but the stars near it always appear 
to be turning round it. Therefore, if we look 
at the Great Bear early in the evening and 
again late at night we shall see that it has 
changed its position ; if we see it again the 
next morning just before sunrise, we shall see 
that it has moved much farther; during the 
day it will be hidden from our view, but if 
we look for it at about the same hour of the 
next evening, it will be found in the same 
place it occupied the evening before, thus 
having gone entirely round the pole. But 
no matter on which side of the pole it may 
be, its stars never change their relative places 
— that is, the Dipper always keeps the same 
form, and the Pointers always point toward 
the Pole Star. 



THE CONSTELLATIONS. 205 

The Pole Star itself forms the end of the 
tail of the constellation called the Little Bear 
(Latin Ursa Minor), which is much like the 
Great Bear, but smaller. It is made up of 
seven small stars, which also are arranged 




The Great Bear and the Pole Star. 



something in the form of a dipper, but it 
is turned a different way from the Great 
Dipper. 

On the opposite side of the Pole Star from 
the Great Bear is the constellation called 
Cassiopeia, formed of five stars of the third 
magnitude and some smaller ones, making a 



206 YOUNG FOLKS' ASTRONOMY. 

figure a little like the outline of a chair. 
These constellations, the Great Bear or Great 
Dipper, the Little Bear or Little Dipper, and 
Cassiopeia, are the three nearest ones to the 
pole ; and when we have learned how to find 
them it will be easy to trace out the others on 
a celestial globe or map, and then to find 
them in the heavens. 



64. The Great Bear, the Little Bear, and Cassiopeia. 

The brightest and most beautiful of the 
constellations is Orion, named after a mighty 
giant and hunter of Greek fable. It is easily 
found by the picture (65) given of it. The three 
bright stars in a line about the middle are 
called Orion's belt. Below it is another row 
of three smaller ones. The two brightest 
stars in Orion are Betelguese (the higher 
one), which looks reddish, and Rigel, a beau- 



THE COXS TELL A TLONS. 



207 



tiful white star. Near Orion is Canis Major 
(Latin for Great Dog), one of the stars of 




65. Orion. 

which, Sirius, is the brightest fixed star in 
the heavens. The ancient Egyptians used 
to believe that when this beautiful star rose 



20$ YOUNG FOLKS' ASTRONOMY. 

in the morning the waters of the Nile began 
to rise also, and so they named it the Nile 
Star, and called the constellation in which it 
was the Dog, because it acted the part of 
a faithful dog in giving them warning of the 
coming of the flood, and gave them time 
to move to safer spots. We stiil call Sirius 




66. The Pleiades. 

the Dog Star, because it was at one time 
believed that it caused very hot weather 
during certain days in summer, which, on that 
account, were called Dog-days. We still 
speak of the Dog-days, but we now know 
that they are not caused by this star. 

The constellations called Gemini (The 



THE CONSTELLATIONS. 20O. 

Twins), Taurus (The Bull), and Eridanus 
(The River Eridanus, or Po) are near Orion 
as shown in the picture. Aldebaran, a bright 
red star, is in Taurus. Taurus may easily 
be known by the Pleiades, a beautiful group 
of stars better shown in the picture (66). 
They are sometimes called the Seven Stars, 
and are said to have been named after the 
seven daughters of Atlas and Pleione, who, 
according to Greek fable, were placed by 
Jupiter in the heavens ; but there are really 
only six stars in the group which can be seen 
by common eyes, and any eye strong enough 
to see seven would probably see four more, 
or eleven stars in all. But when looked at 
through a telescope seventy or eighty other 
little stars can easily be seen. In the picture 
the six brightest stars are those commonly 
seen by the eye alone ; nearly all the others 
need a telescope. The Pleiades, though only 
a part of a constellation (Taurus) and not a 
constellation by themselves, have been more 
important in the past than any other heavenly 
object, except the sun and moon. In ancient 
times many nations made their years, seasons, 
and festivals by their movements, and their 
risings and their settings were watched all 
over the world. 



2lO YOUNG FOLKS' ASTRONOMY. 

The stars of which the different constel- 
lations are made up are not all of the same 
brightness, some being of the first and some 
of the second, third, fourth, and other magni- 
tudes. To distinguish them from each other 
they are marked by the letters of the Greek 
alphabet, the brightest by Alpha (a), the next 
brightest by Beta (/?), and so on. Thus the 
brightest star in the constellation of the Great 
Bear (Ursa Major) is called a Ursae Majoris, 
or in English, a of the Great Bear ; the second 
brightest, /? Ursas Majoris, and so on. When 
there are more stars in a constellation than 
there are letters in the alphabet, they are 
numbered i, 2, 3, and so on. Some of the 
principal stars also have other names, given 
them in early times. For instance, a Canis 
Majoris, or a of- the Great Dog, is the same 
as Sirius ; a Tauri, or a of the Bull, the same 
as Aldebaran, and so on. Thus all the stars 
we have been able to see in the heavens are 
named, lettered, or numbered, so that they 
may easily be found by the aid of a celestial 
globe or map. 

RECITATION FOR LESSON XXVII. 
What is the constellation of the Great Bear more com- 
monly called? 

The Dipper. 



THE CONSTELLATIONS. 211 

Of how many stars is the Dipper made up? 

Seven, four of which form the bowl and 
three the handle. 

Which of these are called the Pointers, and why are 
they so called ? 

The two stars of the bowl furthest from 
the handle ; they are so called because they 
point nearly to the Pole Star. 

Does the Pole Star ever change its place ? 

No ; it is always in the north, at the end 
of the axis around which the heavens appear 
to turn. 

Does the Great Bear or Dipper ever change its place ? 
It appears to be always turning round the 
Pole Star, but its stars always keep the same 
form, and the Pointers always point toward 
the Pole Star. 

To what constellation does the Pole Star itself be- 
long? 

The constellation of the Little Bear. 

Is not the Little Bear somewhat like the Great Bear ? 

Yes ; its stars are arranged also like a dip- 
per, but it is turned a different way from the 
Great Dipper. 
Where is the constellation called Cassiopeia? 

On the opposite side of the Pole Star from 
the Great Bear, and at about the same dis- 
tance from it. 



212 YOUNG FOLKS' ASTRONOMY. 

What is the brightest and most beautiful of the con- 
stellations ? 

Orion, named after a mighty giant of Greek 
fable. 

What is the brightest fixed star in the heavens? 

Sirius. 

What did the Egyptians call this star ? 

The Nile Star, because they thought that 
when it rose the waters of the Nile rose also. 

What name did they give to the constellation in which 
Sirius is? 

The Dog, because it gave warning of the 
coming of the flood. 

What do we sometimes call Sirius? 

The Dog Star, because it was at one time 
believed that it caused the hot weather com- 
monly called Dog-days. 

What remarkable group of stars is in the constellation 
Taurus? 

The Pleiades. 

What other name has it? 

It is sometimes called the Seven Stars, 
though only six can be seen by common eyes. 

Can more be seen through a telescope? 

Yes, seventy or eighty more. 

How are the stars of the different constellations told 
from each other? 

They are marked by the letters of the Greek 



THE CONSTELLATIONS. 21 3 

alphabet, the brightest being called Alpha, 
the next brightest Beta, and so on. 

When there are more stars than there are letters in the 
alphabet, how are they marked? 

They are numbered. 

Have not some of the principal stars names given to 
them? 

Yes ; names which were given them in 
very early times, and are still kept. 



LESSON XXVIII. 

THE JULIAN CALENDAR. 

In the first lesson it is said that astronomy 
enables us to measure time correctly. By 
this is meant that by our knowledge of the 
movements of the heavenly bodies we are en- 
abled to divide time accurately into years, 
months, and days, and thus to make almanacs. 
This division of time is called the calendar 
(Latin calendarium, from calendar, the first day 
of the Roman month, from calare, to call, be- 
cause the Roman priests used to call the peo- 
ple together on that day to tell them of the 
days to be kept sacred during the month). 

We have already learned that the earth rolls 
around the sun once a year, that the moon 
rolls around the earth once a month, and that 
the earth turns on its axis once a dav. Wc 
thus get time divided into years, months, and 
days. By dividing the day into twenty-four 
equal parts we get our hours, which we again 
divide into minutes and seconds; so that all 
our divisions of time depend on the move- 
ments of the heavenly bodies. From this it 



THE JULIAN CALENDAR. 215 

will be seen how very necessary it is that our 
knowledge of astronomy should be accurate. 

In dividing time the most important thing 
to know first is the exact length of the year — 
that is, the exact time of each revolution of the 
earth around the sun ; for if we should get 
this wrong the seasons would come wrong, 
and we might in time have winter in the sum- 
mer months. This really happened in old 
times. The ancient Egyptians gave the year 
three hundred and sixty-five (365) days, when 
it is really about three hundred and sixty-five 
days and a quarter long. This quarter of a 
day made such a difference in the length ol 
the year that in the time of Julius Csesar 
spring came in the time of summer. To reme- 
dy this Cassar got an astronomer named Sosi- 
gines to make a change in the calendar (46 
B.C.). Sosigenes saw that the loss of a quarter 
of a day each year would amount in four years 
to a whole day. So to make the year come right 
he proposed to add a day to every fourth 
year, thus making in every period of four 
years three years of 365 days each and one of 
366 days. We call this fourth year leap year, 
but the Romans named it bissextile year, and 
it is generally so called in the almanacs. 

To understand why this was called bissex- 



2l6 YOUNG FOLKS' ASTRONOMY. 

tile, we must first learn something about the 
months. The Romans began their year on 
the first of March. December was therefore 
their tenth, January their eleventh, and Feb- 
ruary their twelfth month, or the last month 
in their year. At that time every February 
had twenty-eight days, but when Caesar added 
the extra day to every fourth year he put it at 
the end of the year, thus making February 
twenty-nine days long every fourth year. If 
we should add a day to a month, we would 
put it at the end of the month, but the Ro- 
mans counted differently from us. They 
looked upon February 23 as the real end of 
the year, and celebrated it with a feast called 
Terminalia, named after Terminus, their god 
of bounds or limits ; and the five remaining 
days in February were considered a kind of 
interval or space between the end of one year 
and the beginning of the next one. They did 
not number the days of the month as we do, but 
reckoned them backward, counting so many' 
days before each feast day, much as children 
count the days before Christmas. For instance, 
instead of saying February 28, they said " the 
second day of the calends (first) of March;" 
instead of February 27, the third day of the 
calends of March, and so on, always count- 



THE JULIAN CALENDAR, 21 7 

ing the feast day itself as the first day. When 
Julius Caesar added the extra day to Febru- 
ary, he put it after the feast of Terminalia 
(Feb. 23), that is, between the 23d and 24th of 
February, or, as the Romans called it, be- 
tween the seventh and the sixth days of the 
calends of March. As this would change the 
count he ordered that the new day should be 
called a second sixth (Latin bis, twice, and sex- 
tilts, sixth) ; and from this the year which had 
this odd day in it was called a bissextile (Latin 
bissextilis) year, and we have ever since kept 
the name. The calendar thus changed by 
Julius Caesar is commonly called, in honor of 
him, the Julian calendar. 

We also get our names of the months from 
the Romans. January was called by them 
Januarius r from the god Janus; February, 
Februarius, from Februus, the god of the dead, 
because this month was the end of the year ; 
March, Martius, from Mars, the god of war ; 
April, Aprilis, from the Latin word aperire, to 
open, because the buds open in this month ; 
May, Maius, from Maia, the mother of Mer- 
cury ; June, Junius, from the goddess Juno. 
The other six months were at first named ac- 
cording to their number in the year, counting 
March as the first month. Thus, the fifth 



2l8 YOUNG FOLKS' ASTRONOMY. 

month (now July) was named Quintilis (Latin 
quinque, five), the sixth (now August), Sextilis 
(Latin sex, six), the seventh, September (Latin 
septem, seven), the eighth, October (Latin 
octo, eight), the ninth, November (Latin no- 
vem, nine), and the tenth, December (Latin 
decern, ten). After the death of Julius Caesar 
the name of Quintilis was changed to Julius 
(July), in honor of him, and Sextilis was made 
into Augustus (August) in honor of the Em- 
peror Augustus. The others still bear the 
names the Romans gave them when the year 
began on the first of March, and we still say 
September, which means the seventh month, 
though it is really the ninth month of the year. 

RECITATION FOR LESSON XXVIII. 
How do we divide time correctly into years, months, 
and days? 

By means of our knowledge of astronomy. 

What is this division of time called? 

The calendar. 

Why is it so called? 

It is named from caleyidce, the first day of 
each Roman month. 

In dividing time, what is the most important thing to 
know first? 

The exact length of the year, or of the rev- 
olution of the earth around the sun. 



THE JULIAN CALENDAR. 219 

What would happen if we should get this wrong ? 

The seasons would come wrong, and we 
might have winter in the summer months. 

Did this ever happen? 

Yes ; in the time of Julius Caesar, spring 
came in summer. 
What was the cause of this ? 

It was caused by making the year only 365 
days long, when it is really about 365J days. 

How did Caesar change this ? 

He added a day to every fourth year, thus 
making in every period of four years three 
common years of 365 days each, and one year 
of 366 days. 

What is such a fourth year called? 

We commonly call it leap year, but the Ro- 
mans called it bissextile year, and this is the 
name given it in the almanacs. 

What is the calendar thus changed by Julius Caesar 
called? 

The Julian calendar. 

With what months did the Romans begin and end their 
year ? 

They began it with March and ended it with 
February. 

To what month did Caesar add the odd day ? 

To February, so that February has twenty- 
nine days in leap years. 



220 YOUNG FOLKS' ASTRONOMY. 

From what were the months named? 

January, February, March, May, and June 
were named after Roman gods and goddesses ; 
April was named from a Latin word meaning 
to open, because the buds open in that month ; 
and the other six were at first named accord- 
ing to their number in the year, counting 
March as the first month. 

Were any changes made in these numbered months? 

The name of the fifth month of the Roman 
year, at first called Quintilis, was changed to 
Julius (July) in honor of Julius Caesar, and 
that of the sixth month, Sextilis, to Augustus 
(August) in honor of the Emperor Augustus. 



LESSON XXIX. 

THE GREGORIAN CALENDAR. 

The Julian Calendar was used everywhere 
until about three hundred years ago. It was 
then seen that the adding of a day every 
fourth year was too much, for the earth really 
goes round the sun in a little less than three 
hundred and sixty-five and a quarter days, the 
time being very nearly 365 days, 5 hours, 48 
minutes, and 49 seconds. To add one day 
to every fourth year is about eleven and a 
quarter minutes too much, and it was found 
out in time that the seasons had got ahead 
of the true year about ten days. So Pope 
Gregory XIII. ordered in 1582 that ten days 
should be dropped out of the calendar, and 
October 5 of that year was called October 
15 in all countries which were then Roman 
Catholic. Protestant countries were a long 
time in making the change, and in Great 
Britain it was not done until 1752, when Par- 
liament ordered that September 3d should be 
called September 14th, thus dropping eleven 
days, because the calendar was then eleven 



222 YOUNG FOLKS' ASTRONOMY. 

days behind instead of ten. In old records, 
and in many books, dates are often seen with 
the letters 0. S. or N. S. after them ; these 
mean Old Style and New Style, the first being 
according to the Julian Calendar, and the 
second according to the Gregorian Calendar, 
as the new one was named after Pope 
Gregory. The Russians still keep the old 
style, and in their books it is customary to see 
double dates given — that is, the date accord- 
ing to both calendars. For instance, the dif- 
ference now being twelve days, the date July 
4, 1 88 1, would be written in Russia ^^ 1881. 

^ ' July 4, 

In order to keep the year right in the 
future, Pope Gregory made a new rule for 
telling which years were leap years. In the 
Julian Calendar every year whose number 
could be divided evenly by four was a leap 
year; but as this was too many, Gregory 
ordered that each centesimal or hundredth 
year should be a leap year only when it could 
be divided by four after the two ciphers were 
cut off. For instance, 1600 was a leap year, 
because, after cutting off the two ciphers, 16 
can be evenly divided by 4. In the same 
way, 1700 was not a leap year, for with the 
ciphers cut off, 17 cannot be divided by 4 
without leaving a remainder. So the year 



THE GREGORIAN CALENDAR. 223 

1800 was not a leap year, and 1900 will not be 
one ; but 2000 will be one, for 20 is divisible 
by 4 without a remainder. This drops three 
days from the calendar every four hundred 
(400) years, and keeps the calendar year very 
nearly the same as the solar year — that is, 
the time of the earth's movement around the 
sun. The calendar thus changed is called the 
Gregorian Calendar. 

In very early times the year was divided 
into parts according to the revolution of the 
moon around the earth, the time between one 
new moon and the next one being called a 
month. Our word month comes from the 
Anglo-Saxon word monath, month, which is 
made from another Anglo-Saxon word mona, 
meaning the moon. As there are about 
twenty-nine and a half (29-J) days between 
every two new moons, it was found that 
twelve months of this length would make 
only 354 days, or not enough to fill up the 
year ; so the odd days were finally added to 
the months, and now some of them have 31 
days, and the others 30 days each, excepting 
February, which has commonly 28, and in 
leap years 29 days. The number of days in 
each month may be easily remembered by 
learning the following verse : 



224 YOUNG FOLKS' ASTRONOMY. 

"Thirty days hath September, 
April, June, and November ; 
February hath twenty-eight alone, 
All the rest have thirty-one." 

The division of the days of the month into 
periods of seven days called weeks is also 
very ancient. When men thought that the 
earth was the centre of the universe, they 
also thought that the sun, the moon, and the 
planets moved around it. Indeed, they 
reckoned the sun and the moon among the 
planets, so that, with the five real planets which 
they knew (Mars, Mercury, Jupiter, Venus, 
and Saturn), they counted seven planets in all. 
From these seven planets the Romaens named 
the days of the week, as is shown in the fol- 
lowing table, where the names of the Roman 
days are given in Latin, with the translations 
of the names into English, and our names of 
the days: 

Solis Dies Day of the Sun Sunday. 

Lunae Dies Day of the Moon Monday, i 

Martis Dies Day of Mars Tuesday. 

Mercurii Dies Day of Mercury Wednesday. 

Jovis Dies Day of Jupiter Thursday. 

Veneris Dies Day of Venus Friday. 

Saturni Dies Day of Saturn Saturday. 

Thus the Romans gave the names of their 
gods to the planets, and made the days of the 



THE GREGORIAN CALENDAR. 225 

week sacred to them. We have kept these 
old Roman names for three of the days of 
the week, Sunday, Monday and Saturday, 
but we have changed the names of the other 
four. This was done by our Saxon fore- 
fathers in honor of their gods Tuesco or 
Tuisco, Wodin or Odin, Thor, and their god- 
dess Friga. So Tuesday is the day of Tuesco, 
Wednesday the day of Wodin, Thursday the 
day of Thor, and Friday the day of Friga. 

In every common year (365 days) there 
are just fifty-two (52) weeks and one day 
(52X7=364), so that every common year ends 
on the same day on which it began. For in- 
stance, 1 88 1 began on Saturday and will end 
on Saturday ; 1882 will begin on Sunday and 
end on Sunday ; and 1883 will begin on Mon- 
day and end on Monday. Thus, in most 
common years every date in the year is put 
one day beyond the same date of the year 
before. But when a leap year comes this order 
is changed, because the addition of a day to 
February makes one more day in that year, so 
that in the following year all dates will move 
forward two days instead of one day. For 
instance, 1884 will be a leap year, because it 
can be divided by four without a remainder, 
and will therefore have 366 days. As it will 



226 YOUNG FOLKS' ASTRONOMY. 

begin on Tuesday, it will therefore end on 
Wednesday instead of Tuesday, and January I, 
1885, will fall on Thursday, instead of Wednes- 
day as it would if 1884 were not a leap year. 

RECITATION FOR LESSON XXIX. 
Until when was the Julian Calendar used? 

Until about three hundred years ago. 

What was then found out? 

It was found out that the adding of a day 
every fourth year was too much. 

Why was it too much? 

Because it takes the earth a little less than 
365J days to go round the sun. 

What had happened from adding a day every fourth 
year? 

The seasons had got ten days ahead of the 
true year. 

Who made a new change in the calendar? 

Pope Gregory XIII. 

What did he order? 

He ordered that ten days should be dropped 
out of the calendar. 

Was this change made everywhere ? 

It was made in Roman Catholic countries ; 
but Protestant countries were a long time in 
doing it. 

When was the change made in Great Britain? 

About a hundred and thirty years ago. 



THE GREGORIAN CALENDAR. 22J 

How many days was it then necessary to drop from 
the calendar? 

Eleven days, because the calendar was then 
one day more behind than in the time of Pope 
Gregory. 

What is the calendar as changed by Pope Gregory 
called? 

The Gregorian Calendar. 

What do you understand by Old Style and New Style ? 

Old Style is the date according to the 
Julian Calendar, and New Style according to 
the Gregorian Calendar. 

Does any nation still keep the Old Style in its calen- 
dar? 

The Russians still keep the Old Style, and 
in writing dates commonly give both styles. 

What is the difference now between Old Style and 
New Style? 

Twelve days. 

What new rule did Pope Gregory make for counting 
leap years ? 

He ordered that three leap years in every 
four hundred years should be counted as 
common years, and have only 365 days each. 

How do we now tell which of the years are leap 
years? 

All years which can be divided by four 
without a remainder are leap years, except- 
ing the hundredth years ; only those are leap 



228 YOUNG FOLKS' ASTRONOMY. 

years which can be thus divided after the two 
ciphers have been cut off. 

What is the word month made from? 

From the Anglo-Saxon word mona, meaning 
the moon. 

Why was the month named after the moon ? 

Because in early times the year was divided 
into parts of even length, according to the 
revolution of the moon around the earth. 

Do we still follow this plan? 

Not exactly ; we divide the year into twelve 
parts or months, but not of even length. 
Why are the months made of uneven length ? 

Because we cannot divide the year of 365^ 
days into twelve months of the same number 
of days each. 

From what were the seven days of the week named ? 
From the seven planets known to the 
ancients. 

What heavenly bodies did the ancients call the seven 
planets ? 

The sun, the moon, Mars, Mercury, Jupiter,' 
Venus, and Saturn. 

Have we kept the same names for the days of the 
week? 

We have kept only three : Sunday, or the 
day of the sun ; Monday, or the day of the 
moon ; and Saturday, or the day of Saturn. 



THE GREGORIAN CALENDAR. 22Q 

From -what do the names of the other four days of 
the week come ? 

From the names of the heathen gods of 
our Saxon forefathers. 
On what day of the week do common years end ? 

On the same day on which they began. 

What happens from this? 

That every date in the year is put one day 
beyond the same date of the year before. 

What change does a leap year make in this order? 

The adding of a day to February makes all 
dates in the following year move forward 
two days instead of one. 



INDEX. 



Aerolites, 180 

Afternoon, 55 

Air, 27 

Air is blue, 29 

Aldebaran, 210 

Almanacs, 3 

Antarctic Circle, 89 

April, 217 

Arctic Circle, 88 

Asteroids, 140, 145, 159 

Astronomy, what it teaches, 1 

Atmosphere, 27 

August, 218 

Autumn, 82 

Autumnal Equinox, 84 

Axis, 47 

Axis of the Earth, 48, 68, 194 

Axis of the Heavens, 194 

Betelguese, 206 
Bissextile Year, 215 
Bull, Constellation, 209 

CyESAR, Julius, 177, 215 
Calendar, Gregorian, 221 
Calendar, Julian, 214 
Calendar, Russian, 222 



Calends, 214, 216 
Cancer, Tropic of, 88 
Canis Major, 207 
Capricorn, Tropic of, 88 
Cassiopeia, 205 
Centrifugal Force, 148 
Ceres, 160 
Chromosphere, 99 
Circles of the Earth, 88 
Circumference, 24, 25 
Climate, 86 
Coma of Comet, 174 
Comets, 4, 174 
Conjunction, Moon in, 108, 

128 
Constellations, 198 
Corona of Sun, 97 
Crescent, 109 

Dawn, 55 
Day and Night, 53 
Days and Nights, why un- 
equal in length, 71 
December, 218 
Diameter, 24, 25 
Dipper, 203 
Dog Days, 208 



232 



INDEX. 



Dog Star, 208 
Donati's Comet, 178 
Down, Meaning of, 30 

Earth, Ancient ideas about, 

7 
Earth, Annual Revolution 

of, 63 
Earth, Axis of, 68 
Earth, Circumference of, 24 I 
Earth on Columns, 7, 9 
Earth, Diameter of, 25 
Earth, Different Positions of, j 

in Journey round the Sun, j 

76 
Earth, Distance from Sun, 65 | 
Earth in the Heavens, 27 
Earth a Heavenly Body, 2 
Earth, Orbit of, 62, 65 
Earth is round, 13 
Earth lighted by Sun, 54 
Earth, Motion of, shown with ! 

Orange, 43 
Earth moves round the Sun, 

58 
Earth seen from the Moon, 3 
Earth, Shadow of, 19,122,125 
Earth, Size of, 21 
Earth, Size of, compared 

with Moon, 105 
Earth, Turning of, causes day 

and night, 53 
Earth turns round, 40 
Earth turns round once a 

day, 47 



Earth, Two Movements of, 

59 

Earth with Roots, 7, 8 

Eclipse, Annular, 130 

Eclipses, Ancient ideas 
about, 132 

Eclipses, Dates found from, 
133 

Eclipses of Moon, 121 

Eclipses of Sun, 128 

Eclipses, Total, in this cen- 
tury, 130 

Egyptian year, 215 

Equator, 48 

Equinoxes, 83 

Eridanus, Constellation, 209 

Evening, 56 

Evening Star, 157 

Falling Stars, 180 
February, 217 
Fixed Stars, 185, 187 
Flies' Horizon, 13 
Forenoon, 55 
Friday, 224 
Friga, 225 
Frigid Zones, 89 

Galaxy, 188 
Galileo, 165 
Galle, Dr., 169 
Gemini, 208 
Globes, Celestial, 198 
Great Bear, 203 
Great Dog, 207 



INDEX. 



233 



Gregorian Calendar, 221 
Gregory XIII. , 221 
Gravitation, Attraction of, 
33, 146 

Hall, Asaph, 159 
Halley's Comet, 179 
Heat and Cold, 87, 93 
Heat and Light from Sun, 93 
Heavens, Appearance of, 

194 
Heavens, Meaning of the, 

27 
Heavens at Night, 137 
Heavens, Pole of the, 194 
Hemisphere, 49 
Herodotus, 133 
Herschel, Sir William, 169 
Hindoo Earth, 8 
Horizon, 11, 13 

January, 217 

Julian Calendar, 214 

July, 218 

June, 217 

Juno, 160 

Jupiter, 138, 145, 163 

Lamp and Orange, 43, 47, 68, 

71, 87, 121, 129 
Leap Year, 215, 222 
Little Bear, 205 
Lucifer, 157 
Lydians and Medes, Battle 

between, 133 



Magalhaens, 17 

Magellan, 17 

Magnet and Iron Filings, 33 

Maps, Celestial, 198 

Maps, Moon, 114 

March, 217 

Mars, 138, 145, 157 

May, 217 

Medal, Comet, 4 

Mercury, 138, 145, 155 

Meteorites, 180 

Meteors, 180 

Midday 55 

Midnight, 56 

Milky Way, 188 

Monday, 224 

Month, Days in, 224 

Month, Derivation of, 223 

Months, Length of, 216 

Moon, 104 

Moon, Ancient ideas about, 

no 
Moon in Conjunction, 108, 

128 
Moon, Crescent, 109 
Moon, Distance of from 

Earth, 106 
Moon, Eclipses of, 121 
Moon, Full, 109 
Moon, Gibbous, 109 
Moon Maps, 114 
Moon, Motion of, round 

Earth, 107 
Moon Mountains, 115 
Moon, New, no 



234 



INDEX 



Moon in Opposition, 109, 

123 
Moon, Phases of, 108 
Moon seen through a Tele- 
scope, 116 
Moon, Shadow of, 128 
Moon shines by Reflected 

Light, 104 
Moon, Size of, Compared 

with Earth, 105 
Moon, Surface of, 114 
Moon, Two Motions of, 118 
Moons of Mars, 159 
Moons of Jupiter, 165 
Moons of Neptune, 169 
Moons of Planets, 141 
Moons of Saturn, 167 
Moons of Uranus, 169 
Morning, 55 
Morning Star, 157 
Mountains on Earth and 

Moon, 21 
Movement of Heavenly 
Bodies, Apparent, 40 

Nebulae, 189 

Neptune, 138, 145, 169 

New Style, 222 

Newton and the Apple, 37 

Night and Day, 53 

Nights and Days unequal in 

length, 69, 71 
Nile Star, 208 
Noon, 55 
Northern Hemisphere, 49 



North Pole, 48 
North Star, 197 
November, 218 
Nucleus of Comet, 174 

October, 218 

Odin, 225 

Old Style, 222 

Opposition, Moon in, 109, 

123 
Orbit, 62 

Orbit of Comet, 176 
Orbit of Earth, 62 
Orbit of Moon, 107 
Orbits of Plants, 146 
Orion, 206 

Pallas, 160 
Penumbra, 125, 129 
Phases of Mercury and 

Venus, 153, 157 
Photosphere, 99 
Planets, 136 
Planets, Ancient ideas about 

224 
Planets, Attraction of, 148 
Planets, Comparative Sizes , 

of, 139, 144 
Planets, Lesser, 153 
Planets, Motion of in Orbits 

144 
Planets, Names of, 138 
Planets, Table of the, 170 
Pleiades, 209 
Plow, 203 



235 



Pointers, 204 

Polar Circles, 88 

Pole of the Heavens, 104 

Poles, 48 

Pole Star, 197 

Quintilis, 218 

RlGEL, 206 

Rings of Saturn, 166 
Roman Year, 216 

Satellite, no 

Satellites of Planets, 141 

Saturday, 224 

Saturn, 138, 145, 165 

Seasons, Changes of the, 80 

September, 218 

Seven Stars, 209 

Sextilis, 218 

Ships above and below Hori- 
zon, 16 

Shooting Stars, 179 

Sirius, 207 

Sling and Stone Experiment, 
148 

Solar System, 136, 147 

Solstices, 83 

Sosigenes, 215 

South Pole, 4S 

Southern Hemisphere, 49 

Sphere, Meaning of, 49 

Spring, 82 

Star Clusters, 1S9 

Star, Evening, 157 

Star Magnitudes, 187 



Star, Morning, 157 

Stars, Apparent Motion of, 

round Pole Star, 196 
Stars, Changes of, 58 
Stars, Color of, 190 
Stars, Fixed, 185, 187 
Stars are Suns, 186 
Style, Old and New, 222 
Summer, 82 
Summer Solstice, 84 
Sun, 93 

Sun, Ancient ideas about, 8 
Sun, Apparent size of, 94 
Sun, Appearance through 

Telescope, 95 
Sun, Changes of the, 59 
Sun in Eclipse, 97 
Sun, Eclipses of, 128 
Sun, Family of, 136 
Sun, Gases of, 100 
Sun, Metals in, 100 
Sun, Photograph of, 95 
Sun, Spots on, 95 
Sun, Structure of, 99 
Sun Swallowed by Dragon, 

132 
Sun Turns on its Axis, 97 
Sun, Worship of the, 4 
Sunday, 224 
Sunrise, 55 
Sunset, 55 

Table of Planets, 170 
Taurus, 209 
Temperate Zones, 90 



2;6 



IXDEX. 



Terminalia, 216 

Thor, 225 

Thursday, 224 

Time, Measuring, 3, 214 

Torrid Zone, 88 

Transit, 155 

Transits of Mercury and 

Venus, 155 
Tropics, 87 
Tuesco, 225 
Tuesday, 224 
Twilight, 54, 56 
Twins, Constellation, 209 

Universe, Size of, 187 
Up, Meaning of, 30 
Uranus, 138, 145, 169 
Ursa Major, 204 
Ursa Minor, 205 

Venus, 138, 145, 156 



Vernal Equinox, 83 
Vesper, 157 
Vesta, 160 

Wednesday, 224 
Week, Days of the, 224 
William of Normandy, 171 
Winter, 82 
Winter Solstice, 84 
Wodin, 225 

World, First voyage aroun 
17 

Year, Beginning and En 

ing of, 225 
Year, Egyptian, 215 
Year, Length of, 215 
Year, Roman, 216 

Zenith, 195 
Zones, 86 



H 15b 79 




^K 



iilii 

003 630 258 6 



